AGRICULTURAL BOTANY. 431 



were found to be very rich in sodium ehlorid. No positive relationship was 

 found to exist between the formation of water reservoir tissues and the 

 osmotic pressure of desert plants. 



The author concludes that perennial plants of the extreme desert type de- 

 velop a high degree of osmotic pressure, that many of them have the power to 

 regulate this pressure according to the dryness of the region in which they 

 grow, and that both of these characters enable the plants to withdraw moisture 

 from very dry soils. 



Contribution to the study of circulation: Studies on the sweet potato 

 (Ipomoea batatas), B. H. A. Groth (yew Jersey Stas. Rpt. 1909, pp. 3-^3-350, 

 pis. 2). — This paper is a preliminary report of an investigation of the reversal 

 of the water current caused by withholding water from the lower joints and 

 supplying it to the upper ones of a sweet potato vine grown in a hothouse. A 

 piece of the main stem with a side branch was potted and subsequently at 

 intervals of 2 ft. the growing vine and branches were rooted in pots, and the 

 effects of withholding water from the main stem but supplying it to the rooted 

 subdivisions of the branches were noted. 



It was found that a reversal of the water current occurred by which the 

 entire system of the main stem and side branches was enabled to grow from 

 water supplied to the pots in which the side branches were rooted. The roots 

 of the main stem increased in size when in perfectly dry soil, thereby proving, 

 so the author holds, that rooted branches of the sweet potato may, under cer- 

 tain conditions, help to increase the root crop of the main plant. 



On the metabolism of ripening' seeds, W. Zaleski (Bot. CentbL, Beihefte, 

 27 (1911), 1. AM., No. 1, pp. 63-82). — The results are given of investigations on 

 the metabolic changes that occur during the ripening process of seeds as influ- 

 enced by light, dampness, oxygen, and temperature conditions, especially with 

 reference to the nitrogenous compounds formed in the seeds. 



The effect of lig'ht and changes in temperature on the germination of seed 

 and the influence of the water content of the seed in this connection, L. 

 PiCKHOLz (Ztschr. Laiidw. Versuehsw. (Jsten:, Ht {1911), No. 2, pp. 124-151, 

 fig. 1). — The observations made by the author showed that the seed of Poa 

 pratetisis germinated normally in the dnrk only when heated for a time, but 

 that when the heat was applied constantly at either 20 or 28° C, normal 

 germination did not take place. The influence of direct sunlight was mainly 

 due to the heat rays which brought about a temporary increase in temperature. 

 The light rays also were observed to exert a slight influence upon germination, 

 which is considered as possibly due to their transformation into heat. Under 

 constant temperature conditions the seed of Poa did not germinate normally 

 even in direct sunlight when the heat rnys were excluded. The effect of the 

 change of temperature was the same in difS'erent stages of maturity. 



It was further observed that in general the water content of the seed was 

 in inverse proportion to the percentage of germination. In most cases when 

 water was driven off the germination of the seed was benefited, while an 

 addition of water in most cases proved unfavorable, although there were 

 some instances in which it remained indifferent and a few in which it proved 

 advantageous. 



Photosynthesis and the production of dry matter in white and in colored 

 light, W. LuBiMENKo {Rev. G^n. Bot., 23 {1911), No. 265, pp. 1-lJf).— As a re- 

 sult of his experiments the author claims that for the production of dry matter 

 by green plants there is an optimum light requirement, but that its absolute 

 value is less than that which the chlorophyll apparatus needs to perform the 

 maximum of photo-chemical work as expressed by the decomposition of carbon 

 dioxid. 



