General Physiology of the Plant. 207 



panied by a manifestation of heat, a very noticeable 

 instance being the heat developed during the germination 

 of the embryo. 



In order that the various gases used in the metabolism 

 of plants may be supplied as directly as possible to the cells 

 where that metabolism is going on, it is necessary that they 

 should permeate every part of the plant. This they do by 



FIG, 106. INTRRCELLULAR COMMUNICATION OF PROTOPLASM. (Vines.) 



a 1 / 



/ 



a, protoplasm of cell ; 3, protoplasmic threads connecting adjacent cells. 



way of the intercellular spaces and in obedience to the 

 ordinary laws of gaseous diffusion. The stomata aid 

 greatly of course in the entrance of the gases into the 

 interior of the plant, although much of the gas passes 

 directly through the cuticle into the subjacent tissues. 

 Where stomata do not occur as in the Algae, the latter is the 

 only method. 



Having briefly glanced at the various stages in the 

 anabolism of protoplasm,^we-roay A t^v consider its katabol- 

 ism, which must take - place before the energy stored up in 



