1. The influence of varying concentrations of gibberellic acid on seedlings of wheat, lettuce and oats (up 10 days old) was observed and optimal concentration of 10 to 100 μg GA/ml. was established. Biometric evaluation of the experiments showed significant stimulation of the overground parts with all concentrations used (0.1 to 100 μg. GA/ml.) and significant inhibition of bhe roots with concentrations 1 to 100 μg. GA/ml.
2. For lettuce only the concentration 10 μg. GA/ml. was used. In this case, too, increase in length of overground parts was significant and inhibition of root growth was observed. For oats the stimulating effect of GA was recorded for both overground parts and roots.
3. Fresh weight of wheat was stimulated only by concentrations of 100 μg. GA/ml. In the case of lettuce (where values of fresh and dry weight were taken for the whole plant) we found a marked stimulation of fresh weight and a somewhat smaller increase in dry weight.
4. Observation of the dynamics of growth in length of overground parts and roots and increase or fresh and dry weight in lettuce showed a mutual relation between the values recorded in control and experimental plants in the period of 4 to 10 days following germination.

Hemp (Cannabis sativa L.) was sown at intervals from November to August. For each sowing the time of flowering was recorded for male and female plants separately. Male plants usually flowered earlier than female. When the period of daylight exceeds 14 hours, that is when the days are lengthening in April, the female plants stop flowering and continue their vegetative growth. They start flowering again when the days are shortening considerably, in August, when the daylight period is about 15 hours. The male plants flower even when the day is longer than 14 hours.
In experiments during which the plants were shaded it was found that reduction of light intensity leads to an increase in the number of female plants, particularly if shading is carried out in the early stages of the plant's development.
The occurrence of intersexual plants was observed only during the short day period (11 to 13 hours), when they composed 22-30% of the total. When the day exceeds 13 hours intersexual plants no longer develop.
The grafting of plants of varying sex did not produce any sexual change-probably due to the fact that the period of vegetative approximation was short.

1. The symptoms caused by the S-strain(Svobodová 1954, 1958, 1959) were described for ten hosts and compared with those caused by the Al-strain and the ordinary green strain of the tobacco mosaic virus. In all the host plants tested the S-strain produces symptoms different from those caused by other strains.
2. A comparison of the incubation period and the effect on growth ofNicotiana tabacum Samsun, the behaviour onN. rustica and quantitative tests onN. glutinosa showed that the S-strain is the least pathogenic of all the strains compared.
3. Results of biological tests show the S-strain to be most similar to the ordinary green strain of tobacco mosaic virus, only serological and cross-protection tests indicate a closer relationship to the Al-strain, from which it developed.
4. The behaviour of the S-strain of TMV in expressed sap is similar to the behaviour of the ordinary green strain and of the Al-strain. The range of hosts for all three strains is also the same.Physalis alkekengi andP. Franchetti are to a certain extent differential hosts.
Thus biological tests show that the S-strain is a new strain of tobacco mosaic virus.

Für die vorliegende Arbeit wurden die Weizensorte Podbořanka und Těšover Korn benutzt. Der Versuch verlief unter Feldbedingungen bei verschiedenen Pflanzenbestandsdichten. Die schwächste Diehte entsprach der üblichen Norm der Getreideaussaat (400 Getreidekörner auf einen Quadratmeter), die stärkste war fünfmal so dicht. Im Laufe der Vegetationsperiode wurden fünf Messungen durchgeführt. Es zeigte sich, dass die Dichte des Pflanzenbestandes vor allem das Pflanzenwachstum hemmte. Dabei wurden die vegetativen Organe der Versuchspflanzen stärker als die Reproduktionsorgane geschwächt. Eine Erhöhung der Diehte bewirkte zugleich auch eine Herabsetzung des Gehaltes an Chlorophyll, Phosphor und Wasser in den Versuchspflanzen und zwar besonders auffällig gegen Ende der Vegetationsperiode. Die Pflanzen der dichtesten Bestände schöipften weniger Phosphor aus dem Boden, als Pflanzen normaler Bestände. Man kann voraussetzen, dass dies durch eine stark herabgesetzte Sorptionsfähigkeit des Wurzelsystems bewirkt worden ist.

Bei drei Sorten von verschiedener wirtschaftlicher Qualitat, Klarapfel, Wealthy und Ontario, wurde während der Fruchteinlagerung die Vitalität exstirpierter Keime untersucht, und zwar naeh dem Grad der Grünung der Kotyledonen, nach der Wachstumsgeschwindigkeit der isolierten Keimlinge und nach der Wachstumsintensität der Keimwurzeln. Die Beziehungen dieser beobaohteten Charakteristika wurden mittels Faktorenanalyse ausgewertet und mit der als Bioteknose bezeichneten Erscheinung in Verbindung gobraoht.

In homogenates of parts of the plantsCirsium arvense SCOP.,Cineraria hybrida hort.,Reseda odorata L.,Taraxacum officinale WEB. andGladiolus imbricatus L., infected by aster yellows, and inCuscuta europea L., which transferred the aster yellows virus from.Cirsium arvense toPetunia hybrida, similar spherical (polygonal) particles of 30-50 millimicrons, most frequently 35-40 millimicrons, were found. Comparison with homogenates from healthy plants showed that these may be considered to be virospores of the aster yellows virus.

Aphids (Myzodes persicae Sulz.) were subjected to infection feeding after starvation for two hours, in varying air humidities. Infection feeding lasted for five minutes. The aphids which were starved under conditions of 0%, 34% and 56% air humidities transmitted the virus to a greater extent than those kept at humidities of 80% and 100%. (At the relative humidity of 0% there was a slight decrease of infectivity, probably due to reduced activity of the aphids). The phenomenon may be explained by the fact than when denied food in a dry atmosphere the aphids lose more water than in a humid atmosphere and hence their rate of feeding when on the source of infection is more rapid, which tends to increase the number of infected individuals. This finding is regarded as having a practical significance.

The mechanism of the cytomorphological effects of low temperatures was studied by the fixation of young leaves ofTriticum vulgare with temperated alcoholic fixatives. Some specimens were plunged into liquid nitrogen, allowed to thaw and fixed; other objects were plunged into liquid nitrogen and fixed without thawing; control objects were fixed directly. At various temperatures of fixatives (-76, -27,+27,+58° C) different results were observed on the objects pretreated in the same manner. It was thus demonstrated that the destruction processes occur, in this case, during thawing.

The aim of this work was to establish under what conditions the water deficit values obtained byStocker's (1929) method can be considered to be those for actual water deficits. It was found that the water intake of detached leaves is not necessarily due only to incomplete saturation of the leaf tissues with water, but that in young leaves it is caused to a great extent by their extension growth. Thus, water deficit in the sense ofStocker's definition is not merely a simple physiological state of incomplete saturation of the tissues, but is expressed by the sum of the need for water to achieve the greatest possible saturation of the tissues and the need for water in the normal course of the extension growth of cells.

Within one leaf blade there are considerable differences in hydration of its parts. Marked longitudinal, transverse and area gradients of the osmotic pressure of cell sap were ascertained within the leaf blade of sugar beet. The osmotic pressure was determined indirectly by the refractive index according to the empirically established correlation refractive index: osmotic pressure (measured cryoscopically) cf. fig. 1. The gradient from the base of the blade to the tip ranged around plus 40% of the osmotic pressure at the base. This and other gradients mentioned were not noticably changed even when the leaves were artificially saturated with water or when water deficit arose or was adjusted by actual changes in the water balance. (In all these experiments the polarity of the transpiration stream was maintained.) The stability found in various degrees of hydration of individual parts of the adult leaf blade indicates that the variability is a result of the previous ontogenetical development of the leaf as a polar organ and of the fact that the adult leaf remains essentially unchanged by the actual changes in the water exchange. The heterogeneity found in the leaf with regard to the values here dealt with is an expression of the physiological heterogeneity of the leaf blade. ation intensity is concerned, it has been theoretically established that only after the reduction of turgor to nought does increased osmotic pressure of cell sap start to act as a factor in reducing transpiration, and that this reduction is under normal conditions comparatively small (Renner 1915, Stalfelt 1956).

1. Attention is called to the possibility of using resoroin blue for the staining of pollen tubes within the style tissue and the method of staining is described.
2. In pollen tubes, the growth of which is inhibited due to incompatibility, there is at least twice the amount of callose relatively to their length as there is in normally growing compatible tubes. In apple this is primarily due to the greater length of the callose plugs, in tobacco also to their greater density.
3. The regularity of the formation of callose in pollen tubes increases with the rate of their growth.
4. It is suggested that the physiological basis of callose formation consists in the limited capacity of pollen tubes to use the pyran components of metabolized saccharose in the process of respiration.

We have confirmed data regarding the action of γ-hexachlorcyclohexane as an agent inducing polyploidy, established a simple method of its application, determined the extend of its effect and found out whether it would be possible to replace the colchicine technique by a more accesible method of γ-HCH application. The method resulting from preliminary experiments with onion and lettuce was later applied to species and varieties of a number of plants (see list). The activity of γ-HCH as an agent inducing polyploidy was confirmed by the experiments. A method of sowing seeds in a damp film of γ-HCH was projected forLinum usitatissimum, Viola tricolor maxima aLactuca sativa. It seems probable that the use of γ-HCH instead colchicine pretreatment will be possible in cytological technique.

Phosphatase and catalase activity in the woody tissues of grape vine cuttings (Vitis vinifera), stimulated by β-indolebutyric acid, was studied at various temperatures. Its influence is evinced by increased root formation. The cause of the final effect is not, however, only quantitative acceleration of the metabolic processes. The parallelism of the activity changes of both enzymes in the stimulated and control tissues is evidence of this.
β-indolebutyric acid significantly increases the activity of phosphatase and decreases that of catalase.
I wish to thank Prof. Dr. S. Prát for his interest and help. I am indebted to J. Oplt for help in connection with the glass house experiments.

In the course of experiments with leaf samples of pumpkin, sunflower, leafy fodder kale, sugar beet, tobacco, clover and begonia several, methods of storing material were compared with the object of determining the amount of chlorophyll (a+b) after 1 to 3 months. Chlorophyll analyses checked by paper chromatography provided evidence that the most reliable method of serial analyses is the following: Leaf discs are heated in very pure anhydrous acetone to its boiling point (with some MgCO₃ present), rapidly closed with a paraffin stopper and then kept in the dark at temperatures just above 0°C. 50 leaf samples can thus be prepared for storage within 30 minutes. The decrease in total chlorophyll (a+b) content after 28 days of storage does not exceed 5%, after 84 days of storage 10% of the initial value. Chemical conversions of chlorophyll take place here which do not appreciably affect the spectrum of the acetone extract. The method cannot be applied to plants with acid-reacting cell juice (begonia, red varieties of fodder kale and the like). Other practicable methods of storage (a different storage in acetone, storage of fresh samples at +2 to +3°C, drying at +50°C, storage at laboratory temperature) bring about more serious destruction of the pigments.

Parallel measurements of the osmotic pressure (cryoscopic method) and the refractive index of cell sap were carried out on 246 samples from seven plant species. At the same time both values were ascertained as well as their relation for aqueous solutions of some sugars, organic acids and inorganic salts. The relations found with these model solutions are different for different substances. The quantitative composition of osmotically active components of cell sap changes in the course of ontogenesis and as a result the relation of refractive index and osmotic pressure also changes. By this comparison it has been shown that a reliable and more or less linear relation of the two values, which is advantageous for practical application, is only valid for a limited period in the ontogenesis of the experimental plant. The determination of the osmotic pressure of cell sap from the refractive index, the main advantage of which is its quickness and the small volume of sap required (0-02 ml.), is reliable if we construct empiricallyad hoc the appropriate correlation graph for the experimental plant for a limited ontogenetic period.

The work presented in this paper was a study of the influence of different isolated humus substances when applied to the overground parts of plants by spraying on the leaves. The humus components employed showed varying effects on growth, respiration and chlorophyll content inBegonia semperflorens Link et Otto. The result of the physiological changes is reflected in morphological changes of the overground parts and particularly in the structure of the root system. Fulvic acids were found to be the most effective of the humus components when sprayed on leaves.

The author has studied the relation of the catalase activity in thermal blue-green algae to temperature. Experimental data were taken from the first phase of the reaction, so that oxidation of the enzyme by the substrate was eliminated. The relation of the activity of a homogenate of thermal blue-green algae to temperature gives a curve similar to that obtained bySizeR (1944) for pure enzyme preparations isolated from beef livers. The resistance of the enzyme to high temperatures is the same in thermal blue-green algae as in mesopholic seaweeds. The catalase of thermal blue-green algae does not exhibit any special characteristics differing from the catalase of mesophiles.

In der vorliegenden Arbeit ist der Einfluss der äthanolischen Fraktion des Bodenhumus auf das Gleichgewicht der Glycide in isolierten Blättern von Weizen (Triticum vulgare Vill.) Lindě (Tilia cordata Mill.) und Rosskastanie (Aesculus hippocastanum L.) studiert worden.
Es wurde festgestellt, dass die äthanölloslichen Humusstoffe eine Herabsetzung des Gehaltes an nicht reduzierenden Zuckern in den Blättern der Versuchspflanzen und eine Erhöhung der Kohlendioxydausscheidung bewirken. Weil die CO₂-Ausscheidung weder dem Abnehmen der nicht reduzierenden, noch überhaupt aller Zucker entspricht, ist es notwendig vorauszusetzen, dass die äthanolische Fraktion auch andere Umsätze der nicht reduzierenden Zucker unterstützt, welche deren Abnahme in der Blättern bewirken. Ein emfindlicher Indikator des Einflusses der äthanolischen Fraktion ist die Grösse des Verhältnisses N: R (des Verhältnisses der nicht reduzierenden zu den reduzierenden Zuckern), dessen Wert herabgesetzt erscheint.
Ein Versuch mit Kaliumhumat zu Vergleichszwecken zeigte, dass diese Fraktion auf die Pflanzen anders wirkt. Sie setzt den Inhalt der reduzierenden Zucker herab, während die Menge der nicht reduzierenden Zucker eher erhöht wird. Die Atmung erscheint nach 8 Stunden des Versuches nicht wesentlich verändert.
Die äthanolische Fraktion sowie Kaliumhumat erhöhen die Aufnahme von Glukose aus der Lösung durch die Blattstiele der Pflanzen stark.

Der Einfluss der Alkohol-Benzen-Fraktion, der Fraktion der Huminsäuren sowie der Fraktion der Fulvosäuren, die in Konzentrationen von 0,1; 1; 10 und 100 mg je Liter wirkten, äussert sich im Gleichgewichte der Glycide in den oberirdisehen Teilen junger Weizenpflanzen folgendermassen: Die Alkohol-Benzen-Fraktion bewirkt ein Absinken des Gehaltes an nicht reduzierenden Zuekern (N) und ein Ansteigen des Gehaltes der reduzierenden Zucker (R), sodass der Quotient N: R herabgesetzt wird. Dies lässt sich als Anzeichen einer Erhöhung der Intensität katabolischer Vorgänge erklären. Die Fulvosäurenfraktion dagegen erhöht dieses Verhältnis, sodass sich auf eine Erhöhung der Intensität der Synthese schliessen lässt. Die Wirksamkeit der Huminsäurenfraktion ist wenig ausdrucksvoll. Die Beobachtungen dieser Veränderungen korrespondieren mit den Aenderungen des gesamten Trockengewichtes auf solche Weise, dass ein von der Fulvosäurenfraktion bewirkter hoher Quotient N: R mit einem Zuwachs des gesamten Trockengewichtes verbunden ist, während es sein durch die Alkohol-Benzen-Fraktion bewirkter niedriger Wert keineswegs ist.

Some peculiarities of the development of wheat alternatives causing their winter-hardiness were investigated.
1. Prolonged vernalization of wheat alternatives (for at least 80 days) considerably accelerates their development after autumn sowing or after earlier sowing on an artificial short-day regime. Under these conditions the development of alternatives is normally slowed down considerably due to the short day. With rapidly developing vernalized alternatives the growing point is differentiated and shooting occurs in the autumn, which is reflected in the loss of their winter-hardiness.
2. Continuous illumination similarly accelerates the development of alternatives after autumn sowing. As a result of rapid development associated with a differentiation of the growing point and with shooting, winter-hardiness is lost.
3. Low temperatures bring about a change of the reaction of the alternatives to the short day. After vernalization such wheats can develop on the short-day regime. The alternative Noe requires 35 days for the reaction change to take place, the alternatives Česká přesívka and K 26191 require 45 to 50 days of vernalization. In a lesser degree this property may be observed even in spring wheats grown on the short-day regime.
4. The determination of the reaction toward day length showed that the period required is much longer with alternatives than with spring varieties. Thus with spring wheat Lutescens 62 the required period is 21 days, with the Noe alternative 45 days. The same Noe variety sown from vernalized seeds requires 24 days, i. e. almost one-half.

The metabolism of exogenous tryptophane (3. 10^-2M) and β-indoleacetic acid (3. 10^-2M) in extirpated wheat embryos was studied chromatographically and electrophoretically.
It was established that the external application of β-indoleacetic acid in wheat embryos leads to the formation of its complex, indoleacetylaspartic acid. Chromatographical demonstration of the components of the complex was made foliowing alkaline hydrolysis.
A complex compound also arises from exogenous tryptophane, which again frees tryptophane following alkaline hydrolysis. The assumption has been put forward that this is malonyltryptophane, reported by Andreae and Good (Dannenburg andLiverman 1957). The isolated finding of a further substance may be mentioned, which possesses similar chromatographic properties to those of the indole complex-ascorbigen. For reasons so far unknown, this substance has not been isolated again in wheat plants.

Results of the action of low doses of gamma irradiation, intensity 1-80 to 0-24 r/day, are recorded in this paper. Irradiation was carried out on a gamma field with a 0-50 g. equiv. Ra Co⁶⁰ source throughout the whole vegetative cycle.Trifolium pratense var. Jičínský was chosen as the experimental material. Growth and the yield of green matter was followed both on individually bedded out plants and on sown plots. Results of the measurement and weighing of the plants were statistically evaluated by means of the t-test and analysis of variation. Small, daily radiation doses (1.80-0.30 r per day) produced a significant stimulatory effect which was evidenced in the greater height of the irradiated plants as compared with the controls and a higher yield of green matter. In conclusion the paper deals with work that has already been carried out in this field. Experiments and measurements have shown that low doses of chronic gamma radiation are capable of stimulating plant growth. This work is confirmed by result obtained by Breslavets, Berezina and Shchibrya (1956) on other material.

1. During the period from June 11 to August 6, 1957 IEP_M values were recorded for the meristematic tissues of growing points of apex buds of brachyblasts and for phloem and xylem of brachyblasts and growing spurs of apple varieties Transparent Yellow, Lord Lambourne and Watervliet.
2. For a period of 7-14 days before the morphological differentiation of growing points of flower buds the shift of IEP_M values towards the area of higher pH was observed. This shift was found both in the meristematic tissues of growing points and in the phloem and xylem of brachyblasts and growing spurs.
3. After reaching a certain limit a shift of IEP_M values back to the area of lower pH at the original level was observed.

This paper gives a description of a two-channel photoelectric planimeter for measuring leaf areas. It is based on the absorption of rays within the range 0.6 to 1.4μ. The flux of radiation is converted to electric signals by argentum sulphide photocells. The difference in the photoelectric currents from the measuring and control channels is amplified by a sensitive and highly stable d.-c. differential amplifier and is indicated by a meter which can be calibrated direct in area units.

The paper describes a new strain of tobacco mosaic virus which has been named S-strain of TMV because of its characteristic stripe symptoms. The Al-strain of tobacco mosaic virus was used as the initial material.
In contrast to methods used hitherto the S-strain was obtained by interfering with the metabolism of the host plant by a change in the environment. (SvobodovÁ 1954, 1958). The usual hosts of tobacco mosaic virus were used, chiefly tobacco and tomato plants. These plants were cultivated under aseptic conditions on an agar medium in Erlenmeyer flasks with a reduced amount of nutrients, a shortened period of illumination and a limited air supply, so that they were stunted. Following the passage of the initial Al-strain of TMV through these dwarfed plants changes in symptoms appeared, which became apparent only after further passages through plants grown under normal conditions in a glass house in garden soil, where the virus once again had normal conditions for reproduction. Of the new symptoms obtained, only the most striking were further studied (the symptoms of S-strain). By means of alternating of the passage of the Al-strain of TMV from normal-to dwarfed-to normal plants grown under artificial nutrient conditions, i. e. a twice or thrice repeated sudden change of environment, the new strain (S-strain) was obtained five times in all and at different times of the year. From the symptomatic point of view no differences were found in the different repetitions of this change. The results were also the same for material from tomato plants and from tobacco of the Samsun variety.
The origin of the new strain was not caused only by the stuntedness of the host plants. It was also necessary to influence its metabolism by an abnormal environment (particularly insufficient air) in the Erlenmeyer flask before and after inoculation.
Following the reverse passage of the S-strain from plants grown normally in a glass house to dwarfed plants in an artificial environment no further changes occurred. Neither did the passage to ten other hosts grown normally on garden soil and in artificial nutrient produce any further change in symptoms. The S-strain has been maintained by a succession of continuous passages throughNicotiana tabacum Samsun for six years, and each year mass inoculation of a large number of plants is carried out. We therefore now consider the change to be permanent.
Indirect influencing of the virus through a change in the metabolism of the host plant sufficed for the induction of the new strain. Its symptoms appeared only after passage through normal unaffected plants, where the virus reproduction was not inhibited by the retarded growth of the host plant. There is a certain similarity in the emergence of the S-strain and the TM44-stram, obtained byPfanchuch et al., with X-ray irradiation. However, the initial material was the ordinary green strain of TMV.
The biological, chemical and other characteristics ascertained for S-strain and a comparison of these with the characteristics of the initial Al-strain and the ordinary green strain of TMV will be published later.

1. Anagallis arvensis L. (im weiterenA. a.) besitzt eine niedrige Keimfähigkeit, aber lässt sich leicht vegetativ vermehren und pfropfen. Beim Pfropfen "auf die Flasche" ist die Inkubationsdauer kurz, minimal bis 8 Tage. Die Pfropfung "übers Kreuz", das heisst das Durchziehen des abgeschnittenen kranken Stengels durch eine Längsöffnung im Stengel, der gepfropft wird, ist nur theoretisch von Bedeutung.
2. Die Blüten gesunderA. a.-Exemplare schliessen sich bei Nacht. Die fransenförmigen Blüten bleiben länger geöffnet. Blüten mit reduzierten Blütenkronen besitzen nicht abfallende, Monate lang geöffnete Kronen. Bei uns beginntA. a. in der freien Natur gegen Ende Mai zu blühen, im Glashause, sobald die Tageslänge 12^1/2 bis 13 Stunden ausmacht.
3. Der Virusspiegel ändert sich in denA. a.-Pflanzen je nach der ontogenetischen Entwicklung der Wirtspflanze im Zusammenhang mit ihrer Periodizität. Zur Reproduktion des Virus kommt es erst, wenn die Tageslänge mindestens 12 Stunden erreicht hat. Die Viren dieser Gruppe können in den Pflanzen auch latent vorhanden sein.
4. Bei Liptovský Hrádok in der Slowakei haben wir eine FormA. a. mit kleinen rostrot gefärbten Kronen gefunden. Die ersten Anzeichen einer Erkrankung vonA. a. an Vergilbung traten bei uns Ende Juni 1957 und im Jahre 1958 erst Ende Juli in Erscheinung. Die krankenA. a.-Exemplare bilden keimfähige Samen nur in den unteren Kapseln, die sich vor der Infektion entwickelt hatten. Die Virose kann in der Natur einen entscheidenden Einfluss auf die Frequenz vonA. a. haben.
A. a., Stellaria media undVeronica chamaedrys können Indikatoren der Anwesenheit von Viren und Virosen aus der Gruppe der Akarpien sein (Stolbur, Vergilbungen, purple-top und yellow-top bei Kartoffeln).Stellaria media kann als überwinternde Pflanze, die selbst Fröste (mindestens-25°C) verträgt, eine Reservoirpflanze der Viren dieser Gruppe sein.
5. Zu Prolifikationen beiA. a., kommt es von September bis November. Zuerst werden dabei auch die Blüten, später nur die Blätter gebildet.
6. Die Fransenförmigkeit der Blütenkronen beiA. a., kann eines der ersten Anzeichen von Vergilbungserkrankung sein. Es tritt bei übertragung der Hexenbesenkrankheit der Kartoffeln, der green petals der Erdbeerstauden, der Phyllodie bei Kleearten und bei Plantago major in Erscheinung, sowie auch bei Pflanzen, die an bakteriellem Braunwerden der Stengelbasis leiden, sodann auch vorübergehend als mögliche Intoxikationsfolge der fremden Unterlage nach einer Pfropfung gesunderA. a.-Exemplare auf fadenförmige Kartoffelkeime.
7. A. a.-Exemplare, die sehr schwer an Virose erkrankt sind, blühen überhaupt nicht, verzweigen sich aber stark und bilden anstelle der Blüten Blattrosetten.
Verengung, Welligwerden und Anthokyanisierung der Blätter sind nicht immer charakteristische Kennzeichen für eine Vergilbungsvirose vonA. a.
Pfropfreiser krankerA. a.-Exemplare riefen beinicotiana glutinosa wahrscheinlich infolge einer heftigen Intoxikation und eines raschen Absterbens der aufgepfropften Pflanzenteile vonA. a. keine Krankheitssymptome hervor.
Pfropfreiser krankerA. a.-Exemplare bewirkten bei jungen Sämlingen v

Isolated leaf disks are illuminated under constant conditions in a specially arranged chamber and their increase in dry weight within a certain time is taken as a measure of photosynthetic intensity. The weight increment is estimated by comparing the dry weight of the illuminated disks with that of control disks sampled in the close vicinity of the former and dried immediately after sampling. Disks are taken from the leaf blades following a pattern which allows the average original weight of the control and experimental disk sets to be taken as identical within ±0.5%. During illumination in the assimilation chamber the disks are inserted into circular openings bored in agar plates; thus, they remain satisfactorily turgescent throughout the experiment, since they take up water through the section area from the gel. Air from the chamber circulates through a heat exchanger and the concentration of CO₂ is maintained constant in the atmosphere. The chamber is illuminated from above by a set of light bulbs producing an illumination intensity of 1.85×10⁵ erg/cm² sec. It was shown that the dry weight of the disks in the chamber increases proportionally with time for several hours. During this time the effect of injury caused through sampling as well as the conditions to which the disks are exposed in the assimilation chamber, apparently do not interfere with intense photosynthesis. Parallel samples from the same leaves give the same values of dry weight increase; the rate of photosynthesis (dry weight increments) estimated by this method, is thus characteristic for the leaves investigated.

Biological tests of waters combined with determinations of their chemical nature make it possible to classify different types of waters, but usually one figure does not suffice for a correct evaluation of a given water.Gabriel's biological index is a valuable criterion which can give us a good deal of information about the state of the water if the necessary conditions are adhered to; it is not, however, a completely quantitative method and value.
The total body of producers, that is photosynthetizing matter (autotrophs) compared with the total organic matter as a whole [the body of consumers plus reducers (destroyers) plus dissolved organic matter] would be a much better criterion for characterizing the waters than a simple count of various individual bodies, even if this were to be supplemented by the relevant indices.
The usual conventional method, employed hitherto, of a biological oxygen demand must be supplemented by a similarly standardized conventional method of biological production of oxygen.
The literature on the subject gives many different methods for establishing "organic carbon" and chlorophyll; the most important of these have been evaluated critically and experimentally byŠestÁk (1955, 1958a, 1958b). Of a number of tested modifications the procedures outlined in this article proved to be the best. The relationship between producers and consumers plus destroyers must always be simplified. We cannot content ourselves with a figure or an equation, but must respect other factors as far as possible.

1. While studying the inhibitory effects of cadmium ions on the reproduction of tobacco mosaic virus in vivo it was found that a dose of 160 mg. Cd²⁺ applied in two waterings to one plant (immediately before inoculation and the third day following inoculation) produced an average 70% inhibition, without in any way injuring the plants themselves.
2. The inhibitory effect of cadmium ions decreased considerably when the plants were watered with a cadmium ion solution 24 hours before inoculation.
3. The differences in the course of primary infection, as followed by means of iodine tests, were particularly apparent in the following respects: starch is lost from the infected leaves of the experimental plants more slowly, the development of chlorotic spots is slowed down and their delimitation and structure are not so sharp.
4. On some leaves of young tobacco plants (N. tabacum Samsun) larger doses of cadmium produce spots, which resemble the necrotic lesions on leaves ofN. glutinosa following infection with TMV.
5. Preliminary determination indicates that cadmium ions cause a disturbance of phosphorus metabolism.
6. In the discussion it is suggested that the inhibitory effect of cadmium ions on the reproduction of TMV may, analogically to the conception existing in animal physiology, be connected with the interaction of zinc and cadmium ions in nucleoprotein metabolism.

Paper chromatography was applied to the investigation of free sugars present in the vicinity of dormant potato tuber eyelets treated with ethylene chlorhydrin. At the same time aldolase activity was determined. It was shown by the results that the present assumptions on the role of carbohydrates as material for the increase in respiration produced by ethylen chlorhydrin do not conform to actual findings, since the decrease in the starch content in potato tubers during the first phases after exposure to ethylene chlorhydrin is reflected quantitatively in the level of free sugars. The inhibition of aldolase activity prevents further catabolism of free sugars liberated by starch hydrolysis. There is a close agreement between the values of aldolase activity and the sum of the levels of the three quantitatively most important sugars in the potato tuber-glucose, sucrose and fructose. As the aldolase activity decreases the sum of free sugars increases and vice versa. On the basis of the results it is concluded that cardohydrates cannot represent the energy source for a sprouting tuber after ethylene chlorhydrin treatment. It is assumed that trioses and tricarboxylic acids are utilized, i. e. substances whose catabolism is independent of aldolase activity.