288 GLIMPSES INTO PLANT-LIFE 



tion is evident. Briefly, we learn that /;/ /({''/^l the 

 plant gains in weight, whilst /;/ darkness (by respira- 

 tion) it loses. The green plant can only construct 

 growing material out of simple substances in light, 

 having no power to do so in the dark. 



Heat is just as needful to plant-life ; it must 

 be above freezing point, and a somewhat high 

 temperature is necessary to set in miction all 

 those chemi'cal proces.ses that I have briefl}' 

 described. 



At a low temperature the work of assimilation 

 and other processes are arrested ; on the other 

 hand, a rise in temperature increases the activity 

 of these processes. 



We now come to the third function called 

 reproduction. We have seen in connection with 

 the food of plants how they convert inorganic 

 material into organic. This one fact is significant 

 of the great office of plant-life in nature ; animal- 

 life could not exist without its help. I'lant-life 

 may be said to prepare the food of animal-life, and 

 retain that balance of gases in the atmosphere 

 necessary to healthy respiration. How important 

 then it is that all kinds of herbs, trees and plants 



