Physiologie. . 237 



Shreve, E. B., An in vestigation of the causes of autono- 

 mic movements in succulent planis. (Plant World. XVIII. 

 p. 297—312; 331—343. f. 1—11. 1915.) 



Twelve species of Opuntia and Carnegia gigantea exhibit move- 

 ments of stems and branches, which consisi in a drop during de- 

 siccation and a rise during recovery; Ihese movements are correlated 

 v<rith turgidit}' changes. Form of adult cactus plant is determined 

 by water relations existing during period of growth and secondarj' 

 thickening, and not by peculiarities residing in growih point or in 

 mode of initiating branches. Ofuntia versicolor, O. fusicaiilis, and 

 O. leptocaidis exhibit a short-period movement, consisting in an 

 upward movement during the day and a dowmward movement at 

 night, when normal external conditions exist. This movement in 

 O. versicolor is influenced b}' temperature, light, evaporating power 

 of the air, and the water content of both soil and plant. These 

 factors act indirectly, through intermediate processes. The move- 

 ments are caused directly bj' turgidity changes. O. versicolor is less 

 turgid at night than during the da3^ In day absorption exceeds 

 transpiration, while at night transpiration rate is higher than rate 

 of absorption. This is the opposite of the behavior of non-succu- 

 lents which have been studied. Sam F. Trelease. 



Skinnep, J. J., Effect of vanillin as a soil constituent. 

 (Plant World. XVIII. p. 321—330. f. 1—5. 1915.) 



The isolation of vanillin from soils and its harmfulness to 

 plants in Solution cultures has led to a study of its effect as a soil 

 constituent. In pot cultures it was found that a small amount of 

 vanillin decreased greatly the growth of clover. In an infertile soil 

 vanillin was quite harmful to wheat in amounts of 400 — 500 parts 

 per million; in an unproductive sandy loam growth was reduced 

 considerably by 300 — 500 parts per million of vanillin; but no harm- 

 ful effect was evident with the same amounts in a productive soil. 

 In this soil vanillin is probably oxidized and rendered harmless. 

 Field experiments with cowpeas, string beans, and garden peas, 

 grown in a silty clay loam at Arlington, Va., all showed de- 

 creased yield from plots treated with vanillin. Six months after the 

 application vanillin was detected in these plots, and pot cultures 

 showed that it was still harmful to plants. Sam F. Trelease. 



Spoehr, H. A., The theories of photosy nthesis in the 

 light of some new facts. (Plant World. XIX. p. 1—16. 1916.) 



In a critical discussion some of the failings of the formaldehyde 

 hypothesis of photosy nthesis, from chemical and physiological 

 aspects, are pointed out, and experimentation unfettered b}' hypo- 

 theses is urged. Experiments are described by which it is shown 

 that carbon dioxide and water are easily reduced to formic acid by 

 means of light; that from formic acid a sugar-like syrup, analogous 

 to formose, is formed under conditions such as exist in the green 

 leaf; that this substance can serve as the onl}^ source of carbon for 

 the development of the plant; and that plants thrive in an atmo- 

 sphere of formic acid in the light. Sam F. Trelease. 



