THE PLANT AND ITS FOOD 23 



product, but it is so rapidly changed to a 

 more complex molecule that only very minute 

 quantities of it are present at any given instant. 

 Such a rapid change would indeed be antici- 

 pated, as formaldehyde, even in small quan- 

 tities, is a violent poison, that is, it speedily 

 reacts with ordinary protoplasm in such a way 

 as to destroy the intimate chemical archi- 

 tecture of the living substances. The mere 

 fact of its poisonous character constitutes 

 no objection to its occurring as an inter- 

 mediate substance in the synthetic process; 

 we know of many other compounds which, 

 though deadly poisons under certain circum- 

 stances, are still normally present in various 

 phases of the transmutation of substances 

 going on within the plant or animal body. 



Inasmuch as this synthesis of sugar, by 

 means of the chloroplast, is normally dependent 

 on suitable illumination, the process is com- 

 monly called Photosynthesis? a much better 

 term than the older expression, Carbon assi- 

 milation, by which it was formerly known. 



Since Chlamydomonas is a motile organism, 

 it can and does move through the water in 

 which it lives in such a way as to become 

 exposed to the best conditions of illumination. 

 This faculty of taking up a suitable position 



1 Even Photosynthesis is not an altogether satisfactory 

 term, for there are strong reasons for believing that 

 although light starts the process, it is not concerned in 

 the further synthetic processes that result in the formation 

 of sugars. 



