294 



SCIENCE 



[N. S. Vol. XXXIX. No. 999' 



The increase in lipoid phosphorus began earlier in 

 the seed end and increased more rapidly in this end. 

 The decrease in the inorganic phosphorus at the 

 same stage of sprouting occurred in the seed end 

 only. It is interesting to note that in many cases 

 the metabolic activity was greater in the stem half, 

 although the sprouts were all borne on the seed 

 end. 

 Biochemical Study of After-ripening in the Potato 



Tuber: Chas. O. Appleman. 



Under normal conditions potato tubers will not 

 sprout for several weeks after harvest. During 

 this rest period certain changes occur in the chem- 

 ical or physical situation of the buds or their im- 

 mediate environment, which are essential to the re- 

 lease of the growth processes. These changes will 

 be spoken of as after-ripening, using the term in its 

 broadest sense. 



The tubers used in this investigation produce 

 sprouts much earlier from the buds on the seed end. 

 The tubers were therefore cut in half and the 

 analyses made separately on the seed and stem 

 halves with the view to better detect the chemical 

 changes characteristic of after-ripening. 



The carbohydrate transformations during the 

 rest period are dependent entirely upon changing 

 temperature. Active diastase is present at all 

 stages of the rest period and shows no increase 

 during natural after-ripening. Protein, lipoid, or- 

 ganic extractive and inorganic phosphorus, calcu- 

 lated to per cent, of total phosphorus, each remain 

 constant up to the time of sprouting. After-ripen- 

 ing does not involve proteolysis or other changes in 

 the various nitrogen combinations. 



Metabolic changes involving the above substances 

 and some others studied, begin rather suddenly and 

 are concurrent with sprouting. They are, therefore, 

 not primary processes of after-ripening. 

 The Physiology of the Best Period in Potato 



Tubers: Chas. O. Appleman. 



The rest period of the potato tuber is not firmly 

 fixed and hereditary, as it can be entirely elimi- 

 nated by means which will effect a proper adjust- 

 ment between the bud tissue and external agents. 

 The Nutritive Value of Glycocoll to Plants from 



Peat Soils: A. Dachnowski and B. Goemlet. 



In this preliminary statement data are submitted 

 which were obtained from experiments in the lab- 

 oratory with a variety of wheat and with several 

 bog plants, among them Oxycoecus, Scheuchseria 

 and Juncus. Aside from the nutritive inequalities 

 of amino compounds, the attempt is made to de- 

 termine the limiting concentrations of organic and 



inorganic acids and how far fungal mieorrhiza are 

 of importance in any special absorptive powers of 

 plants. 



Twining of Plants as Belated to Withdrawal of 



Light: F. C. Newcombe. 



Various plants when deprived of light lose, in 

 the course of a few days, their power of eircum- 

 nutation, and pursue a straight course, either 

 orthotropic or plagiotropic. This loss of circiun- 

 nutation is not a starvation phenomenon, but is due 

 to a change in geotropic sensitiveness. When the 

 plant is restored to the light, it regains, after sev- 

 eral days, its twining ability. 



Influence of Light on Infection of Certain Bosts^ 



by Powdery Mildews: George M. Eeed. 



An attempt has been made to study the influence 

 of various factors as water supply, temperature, 

 mineral starvation, light, etc., upon infection of 

 hosts by powdery mildews. The results here re- 

 ported relate to the influence of light. 



Seedlings of barley and wheat have been grown 

 in the dark until the first leaf was about 2 to 3 

 centimeters long. The plants were then inoculated 

 with the mildew from their respective hosts. Some 

 of the plants inoculated were kept continuously in 

 the dark; others were removed at once and placed 

 in the light; at intervals of 24 hours other inocu- 

 lated plants were taken from the dark and placed 

 in the light. The general results were that no in- 

 fection occurred if the plants were kept in the 

 dark after inoculation. Upon their removal to the 

 light, infection occurred in proportion to the de- 

 gree to which the etiolated leaves turned green. In 

 general the period of incubation was retarded, 

 proportionally to the time the plants were kept in 

 the dark. 



Another series of experiments was carried out, 

 first growing the plants in the light and then, after 

 inoculation, placing them in the dark, some im- 

 mediately, others at intervals of 24 hours. In the 

 case of the plants placed at once in the dark no in- 

 fection occurred. Those, however, that were kept 

 in the light for one or two days became infected. 

 The period of the incubation of the fungus, how- 

 ever, was materially retarded. In general the ef- 

 fect of the absence of the light upon the mildew is 

 considered to be an indirect one and has to do with 

 the primary effect upon the development of 

 chlorophyll in the host cell. The infection fails to 

 occur in those cells which have not developed the 

 chlorophyll. The mildew then is a strict parasite 

 attacking cells which are not capable of carrying 

 on their normal functions. 



