This paper presents a summary of new evidence for regarding sterility and dwarfing of oats (OSDV) as a virus disease. Brief references are also made to the identification of a further virus in Czechoslovakia-the wheat striate virus (WSV). Both viruses are transmitted by the leafhopperCalligypona pellucida F. The wheat striate virus differs from the oat sterile-dwarf virus in that it can be passed transovarially by the infected females of the vector to their progeny. This characteristic, which made it possible for the two viruses to be separated from each other, was demonstrated for the first time for pathogenic viruses on the European continent in this case. OSDV can be transmitted by leafhopper larvae and adults. The time during which OSDV circulates in the vector's body is very variable; it is usually three to four weeks. The incubation period of OSDV was three to four weeks for oats, four to seven weeks for wheat and barley; rye only showed retarded growth after four weeks. For infection to take place it was necessary for the vector to remain for a minimum of half-an-hour on the test plant; 100% infection was obtained when the vector remained on the plant for three days. The injury inflicted by OSDV on the host does not increase proportionately either with the duration of the feeding period or with an increase in the number of vectors on the plant. Concentrated extracts of the crushed bodies of infectious leafhoppers produced no symptoms of disease, when rubbed or injected into oat plants. Nor were attempts to transfer OSDV and WSV through soil or dodder successful. OSDV was, however, transferred by grafting. Both viruses gave rise to characteristic symptoms inAvena fatua L. andPoa annua L. These findings are discussed from the etiological point of view.

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.

1. Leaves of sugar-beet (Beta saccharifera), which had assimilated active carbon dioxide C¹⁴O₂, were subjected to the process of humification in soil. After three to five months of humification the dried soil was extracted with ether-alcohol, then with sodium or potassium hydroxide; the humic acids were separated from fulvic acids with hydrochloric acid. All fractions were radioactive.
2. Maize plants (Zea mays) grown in diluted Knop's solution with the addition of active humic acid showed radioactivity in the roots and leaves. There was, however, a marked difference between the roots and the leaves. While the activity of the roots after two to twelve days was about 100 to 200 cpm., that of the leaves was about 20 cpm. as calculated for one plant, or about 300 cpm./10 g. for roots and at the limits of measurement for leaves.
3. When a drop of solution and suspension of active humic acid was placed on the lower surface of the first leaf, it spread very little even in this leaf; the activity of the second and third leaves was at the limits of measurement after five days; the same applies to the roots.
4. Autoradiograms were fully in keeping with the results obtained with the counter. Roots were clearly marked and more or less intensely, while the leaves did not appear or appeared only as faint shadows.
5. These experiments do not resolve the question of whether unchanged humic acid penetrates into the cells. It can only be concluded, on the basis of these experiments, that if radioactive humic acid is added to water or to nutrient solution, radioactivity appears in the roots and later weakly in the leaves. If it is assumed that the activity measured in the plant organs was caused by humic acid applied direct, this means that it penetrates into the plant slowly, it is not accumulated and spreads throughout the plant slowly from the roots.

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.

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.

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.