The author describes a method for the determination of water deficit in disks punched out of leaves. The disks, 8 mm. in diameter, are placed on polyethylene rings and saturated in the apertures of a polyurethane foam plate which has been saturated with water (fig. 1, photo 1 and 2). This arrangement makes it possible for the tissue to be completely saturated in 3 hours with a minimum opportunity for infiltration.

Chicory blotch and yellows virus caused yellow local necrotic lesions on the leaves ofChenopodium Quinoa within nine days. Six strains of the common cucumber mosaic virus gave similar lesions in all cases, but in a shorter incubation period.

Chlorophyll formation in etiolated seedlings of wheat and maize, grown for 8 days on Knop's nutrient solution with 10μg. gibberellic acid (further GA) added per ml. was investigated and compared with control plants. Under the light of fluorescent tubes of an intensity of 3000 lux a significant decrease in the amount of chlorophyll (a+b) was observed at all time intervals from 0 to 24 hr., expressed both per dry weight and per leaf length. Experimental results indicate a decreased rate of chlorophyll formation in the presence of GA.
At the same time, a lower content of carotenoids was found in etiolated plants than in controls grown in absence of GA.
The colorimetric determination of the pigments was accompanied by paper chromatography which served as a control of quality and approximate amount of pigments.

Es wird über laufende Arbeiten berichtet.-Bei virösen Erkrankungen gehen dem Auftreten äusserlich erkennbarer Symptome cytologische Veränderungen voraus. Als solche werden u. a. charakteristische Zelleinschlüsse in jungen Keimen von Kartoffelknollen beschrieben. Mit ihrer Hilfe lässt sich nachweisen, dass viröse Prozesse auch in "gesund" getesteten Knollen vorkommen können.-Das unterschiedliche Auftreten spindelförmiger Zellkerne im Palisadenparenchym der Blätter von Solanum tuberosum wird als Zeichen verschieden stark ausgeprägter Neigung zu viröser Erkrankung (Virophilie) angesehen. Versuche zur chemisch-physikalischen Induktion viröser Prozesse ergaben ein bemerkenswertes Auftreten derartiger Kernformen in behandelten Pflanzen.-Die Virogenese wird als ein im Wesentlichen physiologischer Prozess aufgefasst, den die Pflanze gestaltet und der sich sowohl post infectionem als auch autonom entwickeln kann. Das anatomisch nachweisbare Vorkommen virogener Mikroprozesse und viröser Mikroherde macht den Nachweis, dass eine Pflanze virusfrei ist, unmöglich. Vielmehr ist mit der Ubiquität dieses Vorkommens zu rechnen.

From the partial results of artificial cultures in the presence of pistil tissue-pulp the author draws the preliminary conclusion that the inhibitory factor in the pistil ofNicotiana alataLink etOtto is already present before pollination.
These questions were investigated by means of artificial cultivation of pollen tubes on agar in the presence of compatible and incompatible pulped pistils which had been previously prepared in various ways.
This report gives the results of the last series of experiments (part A in the scheme). In the series of earlier experiments no signs of any marked inhibition were recorded.

The study of physico-chemical properties of protopectinase secreted by R. solani was for the first time made and recorded in this paper. The results can be summarised as follows.
1. Protopectinase preparation killed the cells even before maceration was completed.
2. Dilution with water and with autoclaved enzyme solution reduced macerating activity less than toxicity, and thus, indicated that toxins other than enzymes were present in culture filtrates.
3. Protopectinase was highly thermolabile as activity was completely lost after heating for 5 minutes at and above 60° C. When the enzyme was stored at 25° C. for 15 days, there was 80% loss of activity.
4. Protopectinase activity and toxicity was highest at pH 3-4 and there appeared another optimum at pH 7.4.
5. A slight loss of activity occurred on dialysis and was slightly restored by the addition of an autoclaved undialysed enzyme solution. Another peculiarity of the dialysed enzyme solution was that it was most active at pH 6.8 and less active at pH 3.5.
6. Protopectinase was more readily precipitated with acetone than with ethanol. The toxicity of the solution of the precipitate was less than what would have been expected. This again indicated that toxic substances, presumably not enzymic, were removed during the partial purification by precipitation.
7. The addition of monovalent and bivalent salts, particularly in high concentration, to the protopectinase solution resulted in some loss of activity; there was a greater loss with bivalent salts. But soaking test tissue in the salt solutions did not have any effect on protopectinase activity.

1. The aim of the present paper was an investigation of pollen grain size of different species of the Triticum L. natural polyploid series.
2. We determined the pollen grain size of 15 specimens belonging to 8 species. The determination was carried out on permanent acetocarmine preparations.
3. The pollen grain size of differentTriticum species tends to grow with the increasing number of chromosomes. The following mean volumes were computed for the different groups: 62.10³ μ ³ for the diploid group, 96.10³ μ ³ for the tetraploid group (of which 73.10³ μ ³ forT. timopheevi Zhuk.), and 118.10³ μ ³ for the hexaploid group.
4. As can be seen, the volume of the pollen grain does not represent a corresponding multiple of the chromosome number. The reason for this disagreement with the theoretically expected linear relation between the chromosome number and the pollen grain size lies apparently in the allopolyploidy of the polyploid series of the genusTriticum. It seems that the genetically different genoms A, B, D, and G also exert a different effect on the pollen grain size.
5. Our calculations show genom B to have 62%, genom D 29%, and genom G 18% of the effect of genom A (100%). These genoms form a sequence A>B>D>G with respect to their effect on pollen grain volume.

In der vorliegenden Arbeit ist eine einfache Methode beschrieben, mit deren Hilfe es möglich ist, die kritische Bodenfeuchtigkeit ganz objektiv zu bestimmen, bei der die Pflanzen absterben und zwar im Gegensatz zur Bestimmung des Welkungspunktes, die durch subjektive Fehler belastet ist.
Versuche an Sonnenblumen, Bohnen, Mais, Weizen, Buchweizen, Gräsern, Waldholzbäumen und verschiedenen Arten und Abarten des Zuchtweizens zeigten, dass die Bodenfeuchtigkeit, bei der die Pflanzen absterben, bei den verschiedenen Arten und Abarten verschieden ist. Ferner sind andere Arbeiten des Autors zitiert (Stojanov 1955, 1957b, und 1958) in denen er zeigte, dass diese kritische Feuchtigkeit sich nicht nur mit der Dichte der Bestände von Monokulturen, mit der Zusammensetzung der Bestände von Mischkulturen, sondern auch weiter sowohl unter dem Einfluss verschiedener chemischer Stoffe, als auch ihrer Konzentration änder.
Die Werte der Bodenfeuchtigkeit, beider die Pflanzen absterben, bzw. die Punkte des dauernden Welkens sind nicht nur für das Überleben von Pflanzen in der Zeit der Trockenheit wichtig, sondern beeinflussen wahrscheinlich die Ernte auch in Fällen, in denen diese Bodenfeuchtigkeitswerte nicht erreicht werden. Das ergibt sich aus den Untersuchungen vonMaximov undkomiserko, welche zeigten, dass das Pflanzenwachstum vom Abstand (von der Differenz) der Bodenfeuchtigkeit vom Punkte des unzugänglichen Wasser des Bodens abhängig ist.

Weder die Dominanzverhältnisse zwischen den Sprossanlagen noch die Regulationswirkungen der Laub- und Keimblätter, die unter anderem für die vorzeitige Wachstumssistierung namentlich bei den Holzgewächsen verantwortlich sind, lassen sich durch Gibberellinsäure verändern. Doch setzt GS die von assimilierenden Blättern und vegetativen Speicherorganen ausgehenden Hemmungen herab und ersetzt in dieser Hinsicht die Stimulationswirkungen der Wurzeln, allerdings nur unvollständig, da es nachher zu den bekannten Ernährungs- und Gestaltungsstörungen kommt. Auf die Knollenbildung wirkt GS ungünstig, da die Terminalknospe der Knollenanlage zu starkem Streckungswachstum statt zu erforderlicher Ruhe gebracht wird. Die günstige Wirkung von GS auf die Blütenbildung bei der LangkurztagpflanzeBryophyllum crenatum tritt nur dann ein, wenn die mit GS behandelten Kurztagrosetten noch weiter im Kurztag gezogen werden. Somit kommt es hier mehr auf die phylogenetische Anpassung dieser Pflanzen an die Tropen, als auf gewisse stoffliche Einflüsse an, was mutatis mutandis auch von der Rhythmik der Bäume gilt. *** DIRECT SUPPORT *** A01GP005 00005

A description is given of the production of two types of chimera between tomato and nightshade (Solanum koelreuterianum Winkler andS. geartnerianum Winkler).
In the case ofS. gaertnerianum the micromorphological and anatomical characters showed no signs of the significant specific reciprocal effect of one tissue on the other.
The seed progeny of theS. gaertnerianum chimera resembled the control nightshade plants in all the characters investigated.
The following characters were studied: Size of stomata, shape of stomata, shape of trichomes, fruit epidermis, section through the petiole, section through the leaf blade and number of seeds.

Humus acid (Humussäure Riedel de Haen AG. Seelze Hannover) in 0.01% concentration increases the respiration intensity of plant roots grown in water cultures both as regards O₂ consumption and CO₂ production, while RQ (CO₂:O₂) is only very slightly increased. The plants used in these experiments were the winter wheat Pyšelka (Triticum vulgare Vill.), maize Zaj íček's "Český koňský zub" (Zea mays L.) and the gourd Veltrusská velkoplodá (Cucurbita maxima L.). O₂ consumption and CO₂ production were determined on separated root tips by the direct Warburg method. It was found that the effect of humus acid is not only to increase respiration intensity in the roots of the experimental plants, but also their lengths and dry weights (for all experimental plants); for maize and gourd the dry weights of overground parts were also increased, which indicates that increased respiration intensity was linked with more intensive growth of the plants.

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.

A characteristic feature of the effects of humic acids on plant growth is the stimulation of growth in length of the roots. This is sometimes explained as being due to the auxinoid nature of the acids.
The author has examined this assumption by testing segments of wheat coleoptiles and of flax hypocotyls. The growth of segments of both types remained unchanged in solutions of potassium humate in concentrations of 10^-1 to 10^-7 g./l. as compared with the controls in water.
A study was also made of the interaction of humic acids with auxins. The growth curves of segments in concentrations of auxin up to about 20 mg./l. (flax) or 50 mg./l. (wheat) were not altered by the presence of a 10^-1 g./l. concentration of humate in the test solution. With higher concentrations of auxin the growth of the segments in auxin-humate solutions was considerably greater than in solutions containing auxin alone. The effect decreased with rising concentrations of auxins (β-indoleacetic acid and α-naphthylacetic acid).
The auxinoid character of salts of humic acids in water solution was not established, nor was there any confirmation of competitive antagonism in the sense of the antiauxin conception.

The spraying of 26-day-old sunflower plants with a solution containing 50 μg. gibberellic acid/ml. brought about morphological changes in leaves and a statistically significant increase in the leaf shape index (length: width of leaves). The number of leaves on the stem also increased, together with a rise in the value of the ratio of dry weight of stems to dry weight of leaves.

1. In C. olitorius ♀ × C. sidoides ♂, the pod set was 29.4 per cent and the percentage of pod harvested (out of the set pods) was 20 per cent. All harvested pods were empty.
2. In C. sidoides ♀ × C. olitorius ♂, the pod set was 26.8 per cent and that 9.0 per of the cent pods were harvested. The single harvested pod yielded the following types of seeds-4 empty seeds, 9 partially full seeds and 4 apparently full seeds. The apparently full seeds were underweighed. All seeds were non-viable.
3. The pod sets in C. capsularis ♀ × C. sidoides ♂ and in its reciprocal were 31 per cent and 20.0 per cent respectively. No pod remained till maturity.
4. These three species are phylogenetically wide apart.

1. It was found that fluoride has a more pronounced inhibitory effect on the respiration of wheat leaves in plants grown in a solution of gibberellic acid than on that of control plants grown in water, during the entire development of the first leaf.
2. Respiration is markedly inhibited even in old leaves of gibberellintreated plants while the respiration of equally old control plants is stimulated by fluoride by 10-100%.
3. It is assumed that the shift in the equilibrium of respiratory pathways to glycolysis, as is indicated by respiration experiments, is associated with the growth effect of gibberellic acid.

During investigation of amylase activities as continuously variable biochemical features it was found that they are very sensitive to changes in the intensity of vegetative factors. The results of analysis of variance indicate that these characters not only tend to be inheritable themselves, but also the nature and intensity of their reactions to changes in the agro-ecological factors of the external environment show a similar tendency. The actual expression of these features in individuals belonging to a genetically homogeneous group must be considered as the resultant of all reactions of the realisation process concerned, on stimulatory and inhibitory influences, both internal and external. For the genetical analysis of hybrid groups it is necessary to have the most complete picture possible of this continuous modificability which masks the actual genetical variability.
The results obtained in the present investigation provide evidence of complicated relations involved in the hereditary nature and formation of the features under consideration. In further work on the later generations of reciprocal and back crosses it will be necessary to determine more exactly the relative participation of nuclear and plasmatic components both in the hereditary transmission and in the actual formation of these characters.
The present results, although they are only preliminary, confirm the correctness of the modern view in genetics that genetical analysis should be linked with physiological analysis.

Im vorliegenden Beitrag ist eine einfache Methode der Aufklatschchromatographie für die Bewertung des Zuckergehaltes in der Trockensubstanz der Aufklatsche (Aufklatschmasse) beschrieben. Diese Methode ist zum Zwecke der Verfolgung des Spiegels der einzelnen Zucker in den Wurzelspitzen des Weizens ausgearbeitet worden, der in Kulturen mit Humussäurezusatz bei verschiedener relativer Luftfeuchtigkeit wuchs. In der vorliegenden Arbeit ist er am Beispiel der Glukose, unter den Bedingungen niedriger, relativer Feuchtigkeit klargestellt worden. Der Glukosegehalt sinkt mit der Entwicklung der Pflanze bis zum Eintritt der Phase des zweiten Blattes. Während er in der Phase des ersten Blattes bei der Variante mit Humussäure grösser ist, ist dies in der Phase des zweiten Blattes bei den Kontrollpflanzen der Fall,

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.

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.