RECENT ADVANCES IN SCIENCE 227 



scribed by C. E. Salmon in the new Phytologist (Mar. and 

 April). It has the elongated capsules of P. dubium, but the 

 spreading peduncular hairs of P. rhwas. In the same journal 

 N. Carter describes a new species of Trachelomonas. 



PLANT PHYSIOLOGY. By Walter Stiles, M.A., University College, 

 London. (Plant Physiology Committee.) 



Absorption of Water and Dissolved Substances. — A view widely- 

 held in some quarters is that absorption of water and dis- 

 solved substances by the root is limited to the root-hair layer 

 which extends for some distance from a point a little behind the 

 root tip away from the latter. H. Coupin (Comptes rendus, 

 168, 519-22, 1919) has set himself to combat this opinion, by 

 growing seedlings in water-culture so that only 2 or 3 milli- 

 metres of the tip of the main root are in contact with water. 

 Under such conditions the seedlings develop well, and as all 

 the root system except the tip is merely in moist air from 

 which absorption of water is very slight, and absorption of salts 

 non-existent, the absorption of water and dissolved substances 

 through the root tip must take place perfectly readily. 



In the same journal (Comptes rendus, 168» 467-70, 191 9) 

 are recorded the results of some interesting experiments by 

 D. Cebrian de Besteiro and M. Michel-Durand on the effect of 

 light on the absorption of organic matter from Knop's solu- 

 tion containing 0*4 per cent, of sugar. Four different light 

 intensities were employed, ranging from full sunlight to one- 

 ninth sunlight. It was found that increasing the light intensity 

 also increased the quantity of sugar absorbed ; thus the plants 

 in full sunlight absorbed five times as much sugar as the 

 plants exposed to one-ninth sunlight. The hypothesis that, 

 in dull light, plants are better able to utilise root-absorption 

 of organic matter is thus disproved. 



As regards the absorption of inorganic salts, R. B. Harvey 

 and R. H. True (Amer. Journ. Bot. y 5, 516-21, 191 8) have 

 made some observations on seedlings of squash, pea-nut, soy- 

 bean, and sweet-corn growing in solutions of nutrient salts. 

 The concentration of the solution was determined at a number 

 of different times by measuring its electrical conductivity. If 

 the solution is undisturbed, the salts in the culture solution 

 are absorbed by the plant until an equilibrium concentration 



