396 Physiologie. 



more branched tassel, could be correlated with the increasin^ 



nZh^? . H '"'^^^f^'"'' ^"""^ ""^"""^ ^PP"^^- An increase in thi 

 number and size of ears was also noticed. 



G. W. Freiberg (St. Louis). 



^f^FV:.^'^ ßijdragen tot de Physiologie der huidmond- 

 jes van Sacchanim officinarum L. [Contibution s to the phy- 

 siology Ol stomata in Saccharum officinarum L.l. (Meded. 

 Proefstat. Java-Suikerind. V. p. 545-572 1 pl ) ■' ^ ''"''"• 



Kuyper. J., Waarnemingen over de transpiratie van het 



-!!' wf/V'J^o^^^/'^^'^^"^ «" transpiration in sugar- 

 cane]. (Meded. Proefstat. Java-Saikerind. V. p. 573-591. 1 pL) 



99 ^^Ta7S'''i"cS.!''1 '^'''■^ °" ^^^ structure of stomata (Archief, vol. 

 ^ ' P'u u ' ^ ^^^ author now made investigations about the wav 

 mwhich stomata are affected by light, temperature and humidity 

 The results are published in the first pamphlet. In the introduction 

 a Short account is given of the new litterature on the subiect; spe- 

 cial attention IS given to the new American investigators as Briggs 



wnrVnf' /o"!'^^''^' ^ ^ ^ ^^ ^ ' ^annon, Shreve and the 

 work of prof. O. Renner, 



Chapter Ist deals with the method and its application. After 

 some vam trials with other methods, the author decided to use 

 only the paraffineoil-kerosineoil-benzin tesi, first introduced by Miss 

 ü. btem Ihe openmg of stomata is estimated by the rate of ra- 

 pidity with which these several agents penetrate into the leaftissue. 

 beveral hmts are given about peculiarities found in its application. 



What is the mfluence ol light and temperature on the opening 

 Ol stomata; is the question dealt with in the foUowing chapter 

 Uirect sunshme shows itself a very active agent in opening the 

 stomata; darkness prevents opening and causes closure, when the 

 leat Was open before. It seems that prolonged darkness i^ometimes 

 works m this way, that the stomata open to a constant but very 

 low degree. When there is a moderate quantity of light f. i. from a 

 closed sky, the stomata open slowly and generally not to such a 

 aegree as by strong sunshine; this is one of the reasons why sunny 

 mornings are a great profit for cane cultivation. Investigating the 

 influence of darkness a big dark Chamber was used, made from 

 cloth and bamboo, which made it possible to work 6-months old 

 plants m the field. However the dark cloth absorbed such a quan- 

 tity of heat from the tropical sunbeams that the temperature rose 

 to about 43°-45° C; the result of which was, that in stead of clo- 

 sing of stomata by darkness opening by heat happened to occur. 

 When a shelter against the sun was made over the black room the 

 temperature remamed normal and then darkness caused closure of 

 stomata as usual. 



On airhumidity only a few experiments were made; by a high 

 relative humidity the stomata seem to be more opened than by a low 

 one. In the field however a high humidity of the air is almost 

 always connected with and the result of a high soll humidity by 

 rainfall or irngation: in consequence the plant is saturated with 

 water. The higher the rate of Saturation the wider is the opening 

 ot stomata and the longer the stomata remain open under unfa- 

 vourable condition. So it is difficult to see what is the specific in- 

 fluence of a high content of water in the air. 



In another chapter several varieties of cane are compared as 



