The action of zinc on the growth of barley and the biosynthesis of indol compounds and gibberellin-like substances was investigated in a number of concentrations of zinc from doses stimulating growth to toxic doses. The seeds were soaked before sowing in solutions of zinc sulphate (5.10^-5 to 5.10^-1% Zn), and the plants cultivated for 7 days in water. Lower concentrations of zinc increased both plant growth and the biosynthesis of tryptophan and auxins. At the optimum concentration of 5.10^-3% Zn this increase in tryptophan amounted to 241% of the variant without zinc; in substances with an R_F corresponding to indolyacetic acid, the increase determined by the biological test, was 207% as against the variant without zinc. Higher concentrations of zinc inhibited growth, the tryptophan content was decreased to below that of the control without zinc and the auxin content also fell to below the control values. Zinc also influenced the content of gibberellin-like substances in the plants. At a concentration of 5.10^-3% Zn the increase in the growth activity in the gibberellic acid area of the chromatogram was 294% of the variant without zinc. At toxic concentrations of zinc, the content of gibberellin-like substances fell to below that of the controls. The finding that zinc acts simultaneously on the biosynthesis of auxins and gibberellins is also evidence for the common action of growth substances of various chemical types on plant growth.

Comparison with the findings in the cells of other plants and animals showed that the endoplasmic reticulum in the root apex ofFagopyrum has the same general character and function as in other biological objects, i.e. in secretory processes and especially in this case in the transport of the substances produced. Detailed studies of the morphology and activity of the endoplasmic reticulum showed some functional differences which are characteristic for this object. The endoplasmic reticulum participates apparently in the transport of the mass of known but functionally and nomenclatorically controversial formations which here are called dense bodies. Dense bodies exist inFagopyrum in a considerable amount as compared to other objects. Frequent contact of the dense bodies with the ends of the endoplasmic reticulum, contact with the endoplasmic retieulum passing through the plasmodesm, accumulation of the dense bodies along the cell wall and in proximal distance of the plasmodesms and intensive staining of some plasmodesms was observed. The dense vacuoles in this object represent dilated spaces of the endoplasmic reticulum which apparently have the function of reservoirs of the dense mass. The endoplasmic reticulum in the calyptra cells appears to participate in the formation of the cell walls. This object differs hereby from others, where the participation of the Golgi apparatus has been observed in this function.

Substances inhibiting local infection with virus X were isolated from leaves of potato cultivars Saphir, Saco, and Blaník by means of ultracentifugation and were concentrated with ammonium sulphate. These inhibitors were effective if rubbed into leaves of some host plants at least 2-4 days prior to infection without using any abrasives.

The described virus of cow-parsnip,Heracleum sphondylium L., was found in three ruderal localities of Greater Praha. The symptoms are manifested by decolorations which consist of bright yellow areas spreading from the centre of the leaf blade along the main veins. These symptoms appear severely in May. Under higher temperatures and in a chronic stage of infection the symptoms are more or less masked. The disease is mechanically transmissible to parsley, coriander, parsnip, dill, sowbane,Chenopodium quinoa and C.giganteum. The author failed to transmit the disease to celery, carrot, caraway and to 27 species of differential host plants, he failed in the transmission of the virus by the dodder,Cuscuta campestris YUNCK., too. Thermal inactivation point of the virus lies between 51° and 55° C. Infectivity of extracted sap was lost after 2 days at room temperature.

The inhibitor of the X virus (Jermoljev, Albrechtová 1965) can be separated from other proteins by 60 min centrifugation at 40000 r.p.m. in the Spinco L centrifuge and by subsequent gel filtration of the supernatant on a Sephadex G-50 column. For the elution it is best to use Tris-maleate buffers and 0.2M Tris-HCl of pH 7.2. The inhibitor is present in the first fractions containing proteins, between 30 and 45 ml. It is most suitable to concentrate the inhibitor by salting out with ammonium sulphate to 30-50% saturation. The inhibitor can be preserved by adding ammonium sulphate to the sap. At 3°C it can be kept in this manner for 2 months. If the pH of the sap drops below 5.5, the inhibitor is inactivated. Complete inactivation of the inhibitor takes place after a 10 min heating at 67.5°C. No substantial difference in the amount of inhibitor in the sap from apical leaves and leaves from middle levels has been found. Keeping the plants in the dark has no effect on the inhibitor level.

If both cotyledons are amputated from non-decapitated pea seedlings, the intensity of transport of³²P into intact epicotyls is raised more than twofold. This is apparently connected with the regulatory-inhibitory effect of the cotyledons that can be simulated by a 0.1% paste of indoleacetic acid (IAA). If both amputated cotyledons are replaced by this paste, the intensity of³²P transport is again decreased to the level found in plants with intact cotyledons.
When etiolated pea seedlings grown in the dark in 100% relative humidity were decapitated, the³²P transport to the top of the epicotyl stumps covered with 0.5% IAA paste was strikingly decreased if the stumps were covered below with a 10% paste containing chlorocholine chloride (CCC) or with a 0.5% paste containing triiodobenzoic acid (TIBA). On the other hand, the intensity of³²P transport was significantly increased if the IAA paste was put above a 0.5% paste with kinetin which alone does not raise the transport intensity. No such synergism toward³²P transport could be established between IAA and gibberellin.

Antiserum against the X virus inhibitor was prepared by immunizing rabbits with the inhibitor antigen obtained in two ways: (1) ultracentrifugation of potato leaf sap in a Spinco L for 1 h at 40000 r.p.m., (2) ultracentrifugation and fractionation of the sap on a Sephadex G-50 column.
The antiserum is specific against the inhibitor protein and does not react with other proteins of the plant or with the X virus. Direct serological analysis makes it possible to determine in the potato leaf sap either the presence or the absence of the X virus inhibitor, to follow the degree of inactivation of the inhibitor due to various factors and finally to determine the relative amount of inhibitor in various cultivars and hybrids of the potato plant.
A detailed description of the method for determining the amount of the X virus inhibitor in the leaf sap from various potato cultivars and hybrids is given. The amount of sap required for analysis is very small (1-2 ml) which makes it possible to carry out analyses on individual plants. The duration of analysis is about 1 h.
The determination of the inhibitor amount in the potato leaf sap agrees with that of the inhibitory potency of the cell sap in 87.7% cases.

The changes of stomatal and cuticular transpiration of bean plants were investigated by graphical transpiration curves method (Slavík 1958). Bean leaves were infected by fungusUromyces appendiculatus (Pers.) Link. After the infection the intensity of stomatal transpiration had a decreasing tendency. Beginning with the sixth day after infection, the proportion of stomatal and cuticular transpirations becomes more expressive, i.e. the leaves transpire more by cuticles than by stomata. The higher share of cuticular transpiration brings extensive water relations to the diseased plants.

Changes in water uptake immediately following the application of high concentrations of 2-methyl-4-chlorophenoxyacetic acid (MCPA) into the root medium of whole plants ofPisum sativum andVicia faba were investigated potometrically under controlled conditions. It was found that concentrations between 10^-2 and 10^-5 m bring about a sudden, pronounced and lasting inhibition of water uptake. Its rate depends directly on MCPA concentration. At 10^-2 m, sudden inhibition of water uptake becomes apparent as early as 10 min after application. With decreasing concentrations the appearance of inhibition is retarded but the inhibition is still sudden and well-pronounced. The inhibition of water uptake observed after MCPA application to the root medium of whole plants agrees with the sudden striking reduction in transpiration intensity observed byAllerup (1964) after the application of similar concentrations of 2,4-dichlorophenoxyacetic acid. The presence of MCPA in the nutrient medium causes inhibition of water uptake even in cut plants. Its rate again depends on the concentration of the growth substance. The inhibition does not appear here as quickly and is not as sudden and pronounced. High concentrations of MCPA during application to over-ground plant organs do not bring about immediate inhibition of water uptake by the root.

The content of endogenous gibberellins was determined chromatographically in the roots 14-17 days old pea seedlings cultivated in water cultures in the dark. When the epicotyls are amputated from these plants, the content of endogenous gibberellins increases significantly within 6-12 hours after amputation as compared with the intact controls, then it falls off again considerably up to 24 hours after amputation. The initial increase of the gibberellin level in the roots can be explained by transport inhibition of the endogenous gibberellins from the root to the epicotyl, the later decrease of this level to be interpreted as inhibition of auxin transport from the epicotyl into the root. This is supported by the observation that spreading of a 0.5% paste with IAA over the epicotyl stump immediately after amputation prevents the mentioned decrease of the gibberellin level in the roots, whereas this decrease is intensified by using a paste with TIBA which inhibits the auxin transport. The results of this work support the possibility of direct gibberellin synthesis in the roots.

In experiments with fodder cabbage and sugar beet the influences were tested which restrict the finding of a uniform linear dependence between the chlorophyll content and photosynthetic rate. The main factor is most probably the irradiation during the growth of plants and the measuring of photosynthetic rate. Changes in the density and length of irradiation with the proceeding spring season are reflected in the decrease of unit chlorophyll activity in all leaves of the plant. Such differences were not observed in plants grown in winter months at a low greenhouse irradiation density. High irradiation density during the measurement of photosynthesis ensures the finding of high correlation of photosynthetic rate with the chlorophyll amount per unit area of leaf. With a low irradiation density, or in thick leaves, the lower layers of chloroplasts are not saturated with radiation, and hence a higher correlation coefficient is found by relating photosynthetic rate to the percentage of chlorophyll in dry weight than to the quantity of chlorophyll per unit area of leaf blade. In some experiments higher activity of chlorophylls was found in young leaves before they have reached the state of "photosynthetic maturity" than after this turning point. This difference diminished by relating the photosynthetic rate to chlorophylla content instead of the total amount of chlorophylls (a+b). High activity of chlorophylls in very young leaves and great individual variability within the experimental plant groups caused by uneven cultivation conditions are the basis of apparent sigmoid character of average curves for the chlorophyll-photosynthesis relation.

It was shown that in the horse bean seeds (Vicia faba) the cotyledon proteins are identical, from an immunochemical standpoint, with those coming from the extracotyledon parts (radicle, young stem and embryonal leaves, in totality). However, the beginning of the germinative process exerts a different influence on the antigenic properties of the constitutive parts of the seed. The modification of the antigenic structure in cotyledons takes place slowly. On the contrary, in the extracotyledon parts a rapid decrease was found of the number of antigens present in the non-germinated seed. As the organs become differentiated, the hydrolysis process of these antigens goes on until their almost complete exhaustion. However, it appears that three of the initial antigens remain in the newly arisen leaves. Besides these antigens there are also specific-organ antigens which appear as the respective organs become morphologically differentiated. It was found that in the growing leaves the process of photosynthesis induces the synthesis of antigens characteristic for the mature leaves. The organ-specific antigens occur during plant development at the time when the leaf attains the morphological structure and the functional specialization characteristic for maturity.

The dense vacuoles, considered to be the classic Golgi apparatus in the root meristem ofFagopyrum, were studied by the following methods: 1. Impregnation methods for the demonstration of the Golgi apparatus, 2. cytochemical methods, 3. electron microscopic methods in the light microscope and 4. the electron microscope. A comparison was made with the classic Golgi apparatus in animal cells in the light and electron microscope.
Dense vacuoles inFagopyrum and also evidently in other plants, were taken for the classic Golgi apparatus on account of their morphological similarity to the Golgi apparatus in animal cells on impregnation with silver and osmium and their staining preperties with lipoid methods. Dense vacuoles differ from the classic Golgi apparatus in other chemical properties, such as content of phenol substances, etc. No formations were found in animal cells which were similar to dense vacuoles on investigating by electron microscopy. In the electron microscope dense vacuoles have the appearance of derivatives of the normal light vacuoles known in plant cells. They therefore belong to vacuome of plant cell and cannot be analogous to the classic Golgi apparatus in animal cells. Thus the use of the term Golgi apparatus for dense vacuoles is not well founded.
A comparison was made of fixation and impregnation used in the light microscope with fixation in the electron microscope. After fixation with permanganate, dense vacuoles have the same shape as after impregnation. After fixation with permanganate, they stain an intense black in the same way as after impregnation with silver and osmium. The form of the vacuoles is dependent on the fixation used. The comparison was made in the light microscope.

It was observed that the polyploids ofTrigonella foenum-graecum produced by seed treatment with 0.2% colchicine died after two cotyledonary stage, while the ones produced by seedling treatment survived. The root and shoot of seed treated plants were found to be mixoploids. The root tips exhibited 2n to 12n chromosomes and with the passage of time there is a regular decrease in the frequency of cells with lower chromosomes. The frequency of dividing cells decreases considerably towards the end of the 6th day due to the highploidy of most of the ploid plants. In case of seedling treatment the first formed tissue was mixoploid of high level similar to that of seed treated ones but in some cases the growing tip reverted to low level of ploidy which lead to more or less normal growth.
Since the difference in the constitution of seed and seedling treated plants lies in their root system, it has been suggested that probably highploidy of root system in the former may be responsible for the 100% mortality of plants.

The transmission of carrot mosaic virus (CMV) by the crude sap to 11 varieties of plants from 4 families was demonstrated. From these plants the virus could be transferred back to a healthy carrot cultivated from the seed in isolation. The incubation time required for the appearance of the symptoms of CMV was 7-20 days. The plants on which mosaic or spot symptoms appeared on the leaves after transfer by the sap at temperatures below 15°C remains habitually healthy after the transfer of virus at higher temperatures.
The results of the mechanical inoculation of CMV by the crude infectious sap to young carrots cultivated from seeds differentiated this virus fromApium virus 1, which after mechanical inoculation causes chlorosis of the youngest carrot leaves in contrast to CMV. A further differentiation of CMV fromApium virus 1 is shown by the fact that CMV can be transferred only to the familyDaucaceae. It differs in this fromApium virus 1 which is transferred exclusively to this family (Köhler, Klinkowski 1954). CMV is differentiated fromCucumis virus 1/Doolittle Smith by some different host plants.

Investigating weeds for viruses in ruderal localities of Greater Prague two forms of mosaic diseases inSisymbrium loeselii Jusl. were demonstrated (green and yellowish-green mosaic). Transmission tests carried out on differential host plants showed that the green mosaic is caused by cabbage black ringspot virus (CBRV) and the yellowish green by mixed infection of CBRV and tobacco mosaic virus (TMV).
TMV-isolate is characterized as an unusual necrotic strain; its capability to reproduce in cruciferous plant in nature is unique.
It was ascertained that green mosaic was commonly spread overSisymbrium plants in ruderal ***DIRECT SUPPORT *** A01GP029 00004 associations on Prague territory; epidemiological significance of this discovery is discussed.

The exposure ofTaraxacum officinale L. at flowering time to a weak magnetic field resulted in (1) retarded opening and the closing of the inflorescence, (2) wilting and death after prolonged exposure. Controls were unchanged. Plants exposed to the effect of magnetic fields were degenerated in subsequent year.

Plants of two varieties of winter wheat-Besostoya 1 and Etoile de Choisie- were raised in the field. The same number of selected plants from each variety were frozen once in a refrigerator at a temperature of -15°C for 24 hrs. After freezing, the plants were gradually thawed and returned to the field. Early in the spring, test and control plants were treated with one of following diluted solutions: vitamin B₁, vitamin B₆, indolyl-3-acetic acid and adenine (the four solutions at a concentration of 0.01% and 5% urea solution in water) by immersion for 15 hrs. at a temperature of 18-20°C. The plants were measured in the spring and in the summer, the yield being determined after ripening.
It was found that all substances used helped to diminish the deleterious consequences of overwintering and to raise the yield of the plants. Vitamin B₆ exerted the strongest influence. Vitamin B₆ treated plants produced higher or slightly lower yields than those of the non-frozen control. Plants treated with vitamin B₁ gave yields close to, but in most cases lower than those of the non-frozen control.
The yields of plants treated with solutions of the remaining substances were appreciably lower than those of the non-frozen controls.
Plants of the more winter-hardy variety Besostoya 1 recovered relatively more easily under the effect of the substances used than the plants of the less winter-hardy variety Etoile de Choise.

A study was made of the anatomical structure of the shoot apices ofHyoscyamus niger L. in plants which were transferred from a long-day to a short-day regime after the initiation of the inflorescence. After a certain time these plants are reverted to the vegetative stage with the inhibition of the development of further flower buds and the renewed production of rosette leaves. The inflorescence apex consisted of a few superficial layers of cells and a corpus composed of slightly elongated cells. The anatomical structure of the apices which were reverted into the vegetative state resembled that of shoot apices in the intermediate stage. The apex had several layers of small cells, under which there was a group of small but irregularly arranged cells which passed into the rib meristem.
The shoot apices of plants transferred from a long to a short-day regime at different time intervals after fulfilling the requirements of minimal photoperiodic induction thus, on the short day, display morphological and anatomical characteristics of various degrees of transition from generative to vegetative stage.

The effect of the individual leaf blades of spring wheat on the dry matter of stalks, chaff and grain (caryopses), of spikes and total overground part, was studied. In the experimental plants the individual leaf blades were detached according to the scheme given, at the beginning of shooting, (A), at the beginning of earing (B), and at the beginning of flowering (C). The dry matter (fresh weight) of the stalk was least decreased if either the lowest or the uppermost leaf blade was severed during the developmental phase of shooting. The dry as well as the fresh weights of chaff were least affected in those plants where the leaf blade was removed during the developmental phase of flowering. Both the dry and fresh weights of caryopses were least decreased if either the lowest or the uppermost leaf blade was removed during the developmental phase of flowering. The dry weight as well as the relative water content of chaff and ear grains were most decreased following removal of leaf blades during the developmental phase of shooting. The relative water content of chaff, grains and ears was most decreased following removal of developed leaf blades during the developmental phase of earing. It was confirmed that in addition to the photosynthetic activity of leaves the photosynthesis of other parts of the stem system (stalk internodes, ear awns etc.) participated in the production of total dry matter of experimental plants. The photosynthetic activity of leaf blades was particularly high up to the earing phase, while subsequently the photosynthesis of extrafoliar area (stalk internodes and ears) predominated. In spite of this, participation of the total leaf area is very high in the formation of grain dry matter (over 50%), as well as of the total dry matter of plant (over 80%).

When the epicotyl and one cotyledon is cut off from pea seedlings, only the axillary of the amputated cotyledon is known to grow. When³²P is applied to the roots of such plants, then a higher radioactivity appears in the axillary of the amputated cotyledon already 24 hrs. after amputation of one cotyledon, although this axillary is of the same size at this time as that of the remaining cotyledon. This fact indicates a more extensive material transport to the axillary bud of the amputated cotyledon already during the first day after amputation
The effect of individual regulators on the³²P transport was investigated in an experiment where pea seedlings cultivated in the dark were decapitated and a 0.5% paste, containing the regulatory compounds was placed either on the cutting surface in the apical part of the epicotyl stump or in its central part. After a week the plant roots were supplied with³²P and its transport to the upper part of the epicotyl stump was followed. This transport increased about 10-fold in the case of a paste, containing indolyl acetic acid, when the paste was spread on the apical cutting surface of the stump. However, the transport was inhibited when the paste was applied in the central part of the stump. These results indicate that only the transport of³²P towards the paste with indolyl acetic acid is accelerated, whereas it is decelerated above this paste. A paste, containing triodobenzoic acid inhibited³²P transport only when applied to the apical cutting surface of the epicotyl stump and not when spread over the middle part. In this case³²P transport was more rapid above the paste than towards the paste. The situation was similar in the case of gibberellin and kinetin.

The effect of different exposures to RTG radiation (100 r, 250 r, 500 r, 1000 r, 2500 r, 5000 r) on the changes of the permeability of the epidermal cells ofAllium cepa L., variety Všetaty, bulbs was studied during three vegetation periods. Bulbs from growing plants (followed from the development phase of bulb growth) and bulbs immediately after harvesting were used for the experiments.
It was demonstrated in our experiments by plasmolysis that the radiation-induced changes of cell permeability were irreversible. When plasmolytic agents of non-electrolyte character (1M sucrose, 1M glycerol, 1M urea) were used, the equilibrium state (total plasmolysis) was reached more rapidly with the irradiated bulbs than with the unirradiated controls. When electrolytes were used (0.5M KNO₃, 0,5M KBr), total plasmolysis occurred less rapidly with the irradiated objects than with the controls. These relationships were manifest during the whole ontogenesis ofAllium cepa L. An exposure to 100 r was sufficient in our experiments for causing the mentioned changes, proving a considerable sensitivity of the osmotic properties of the epidermal cells ofAllium cepa L. bulbs to ionizing RTG radiation.
Plasmolytic experiments after smaller exposures than 100 r of RTG-rays are in preparation.

In a previous communication (Bartoš, Kubín andŠetlík 1960) a method was reported, which makes it possible to measure the average rate of photosynthesis in a representative sample of a large number of leaves. The sampling is made by cutting out disks of leaf tissue, following a definite pattern. Isolated leaf disks are then illuminated under controlled conditions and the rate of photosynthesis is estimated by weighing the increment of dry matter in a given time interval.
Data published in the present paper demonstrate that this method can be successfully used for a characterisation of photosynthetic capacity (specific rate of photosynthesis, seeBartoš, Kubín andŠetlík 1960). Both specific values for individual plants and average values for homogenous plant populations may be estimated with very good accuracy. One of the chief factors which render this possible is obviously the surprising homogeneity of the photosynthetic tissue of leaves. Samples of very small size may serve as representative of a large total leaf area, e.g. of a population under field conditions.
Preliminary results of comparative investigations suggest that, with the plant varieties examined, differences in photosynthetic capacity are not very great, both between and within populations of diverse varieties. Differences as large as 50% have been encountered so far solely between values of photosynthetic capacity estimated for individual plants in a population. On the other hand, values of average photosynthetic capacity in populations of crop plant varieties within one species or genus are, as a rule, not very distinct and quite often no statistically significant difference can be demonstrated in such cases. Even if the varieties belong to different genera, differences in photosynthetic capacity in their populations greater than some 50% have been found only as an exception.
In considering all these results one important fact must be taken into account, i.e. the intensity of illumination in the apparatus. Contrary to what was intended and awaited, the radiation intensity used was not high enough to saturate photosynthesis in leaf disks. The light dependence of photosynthesis in isolated portions of leaf tissue apparently has a somewhat different character from that usually assumed for intact leaves of higher plants.

Experiments with isolated wheat roots and with intact wheat plants showed that glutamic acid decarboxylase from the roots takes part in the transformation of substance in the medium and that its activity is influenced by the medium. Glutamic acid decarboxylase is thus a factor taking part in the formation of substances excreted by the plants roots.

Plants of ten varietal populations of maize and their progenies in S₃ generation had been evaluated for their resistance to sources of corn smut in conditions of increased infection level. According to the infection degree, the experimental material was divided into classes (I-V) corresponding to five categories of resistance.
The relative representation of progenies from populations differing in their susceptibility to the parasite in their particular classes showed that the heterozygous varietal populations posses some imunological structure.
1. In the composition of the populations the resistant forms prevail over the susceptible ones. In the populations studied 82.8-98.5% dissected at selfing were grouped into classes I-III.
2. The basis of resistance of populations is formed by a group of forms ranged into the second class of resistance. This group being equally represented in all populations (31.1-40.8%) independently of their susceptibility to corn smut.
3. The differences in disease attack of plants of the particular populations had been influenced by the relative participation of selfed progenies, ranged on the one hand into class I and on the other hand into classes III and IV. The occurence of progenies in these categories in populations arranged consecutively from higher to lower resistance varied in conformity on extent 46.2-15.5%, 11.5-37.5% and 1.5-17.8%.
The experimental data showed, among others that the general smut attack of plants in populations (23.5-49.6%) corresponded in most instances to the average attack of progenies in S₃ generation (21.0-44.2%).

The part of the radioactive fractions of humus substances which is soluble in alcohol (or in ether) spreads from drops of solution or from a mixture with lanoline paste mainly through the vascular bundles. The active component of humic acid evidently does not spread in the leaves, while the active component of fulvic acids fails to penetrate the tissues of some plants, but in others spreads to a distance of several centimetres.

Lucerne plants in the first crop year as well as plants of spring wheat from different sites of the respective experimental plots showed differences in sap exudation from detopped roots or from stumps of the main shoots, reflecting differences in properties of the soil profile. The differences in sap exudation were observed at a time when the plants did not show any visible differences in water availability.
Differences in the water potential deficit of the leaf blades of lucerne plants in the second crop year and of sugar beet plants, related to differences in soil profile properties, were observed in another series of experiments. Sugar beet plants showed a higher physiological lability than lucerne plants.
The sites characterized by unfavourable plant-water-relations usually gave lower yields. The coefficients of variability for the yields of lucerne fresh matter from irrigated plots were three times lower than those for yields from plots without irrigation, influenced by soil heterogeneity.

Decreasing the illumination intensity of winter and semi-winter varieties of wheat to below a certain limit led to an accelerated development of the shoot apex of the main axis, whereas the development of spring varieties was slowed down. In plants whose development was accelerated by decreasing illumination intensity, the dry weight of the overground parts was smaller and the carbohydrate content of the shoot apex of the main axis was greater than in control plants growing under normal conditions of illumination. Plants subjected to long vernalization developed more rapidly and the weight of the overground parts was less than in plants subjected to vernalization for the normal time. The accelerating effect of decreased illumination intensity on plant development is explained by a changed manner of growth which is connected with a greater flow of assimilates to the shoot apex.

The different components of humus-alcoholic extract, humic acids and fulvic acids-progressively isolated from compost garden soil and deprived of minerál ions by electrodialysis, were, after addition to Sachs's nutrient solution, found to have differing effects on the growth of stems and roots of tomato plants. Similarly, differences in the effect on oxygen intake of leaves and roots was confirmed and varying amounts of chlorophyll were determined in the leaves. Fulvic acids were shown to be more active components of humus than humic acids. Morphological changes in the root system were found to be more typical for an estimation of the action of the different components of humus than the changes in physiological characteristics mentioned above.

Quantitative determination of chlorophyll a and β can be made by paper chromatography of acetone extracts of plant material with colorimetric measurement of the eluates from the separated zones.
From the suitable solvent systems which give adequate separation of the pigments at a distance of 20 cm. from the start,Hager's mixture (1955) separates the chlorophylls better than the toluene-isopropanol (400: 1 v/v.) mixture, which, however, is better for the separation of carotenoids. Twice the amount of chlorophyll is separated on Whatman 31 ET paper, equally well and with the same time of development, as on Whatman No. 3 paper, on which it is possible to separate a maximum of about 15 μg of chlorophyll pigments per 1 em. start length. Losses on elution are, however, higher on using Whatman 31 ET paper. In plants with a high chlorophyllase activity, the error of determining chlorophyll a andb is greatly reduced if the leaves are placed for 1 min. in boiling water before extraction. For elution of chlorophylla andb from paper it is better to use anhydrous acetone, for chlorophyllides 80% acetone.
A comparison of the procedure investigated with the method of two-wave length spectrophotometric measurement of crude acetone extracts showed that in view of the average 10% loss, the chromatographic method is hardly suitable for determining the absolute amounts of chlorophylla andb, although the relation (a/b) can be determined with similar precision by both methods. Moreover, in view of the greater amount of work involved the chromatographic method can only be recommended for confirming the results of spectrophotometrie determination. Quantitative determination of chlorophylls from the area of the spot or from the "R_F" value can only be of an informative character.