316 s. KUSANO : TRANSPIRATION OF 



Subsequently, Lidforss^^ found that the guard-cells of the 

 storaata on the leaves of some winter-green plants which he 

 examined, were free of starch during winter, and that this 

 absence of starch rendered the stomata incapable of performing 

 their normal function. 



Although I have not made an extensive study of this jDoint, 

 that is to say, to the extent of examining in each given case 

 whether the stomata were surely closed or not, I have reason to 

 conclude, so far as my observations extend, that many of our 

 indigenous evergreen trees, unlike those of Germany above 

 referred to, have their stomata more or less open even in the 

 midst of winter. This condition may probably be considered as 

 one of the chief causes which make the amount of the winter 

 transpiration of our evergreen trees considerable. 



II. Method. 



The amount of water transpired by plants may be deter- 

 mined in various ways : first, by weighing the plants themselves 

 at definite intervals ; secondly, by condensing the vapour which 

 is given off from the plants and measuring its volume ; thirdly, 

 by measuring the increase of the weight of some hygroscopic 

 substances, like calcium chloride, by which the vapour derived 

 from the plant is absorbed ; and fourthly, by measuring the 

 amount of water absorbed from the root or cut-surface. Of these 

 four methods, only the first and the last were adopted in my 

 investigations. 



])Lidrorss, Zur I'liysiologic und Lldlogio dor Wiiitcigriincn Flora. But. Ct'iillbl., lÀl. 

 LXVIII, 18%, p. 35. 



