COMPOUND ORGANISMS 189 



Nevertheless it has not wholly lost its chloro- 

 phyll, and it is of special interest to find that 

 if it happens to grow where it cannot obtain 

 plenty of nourishment from its host plant, 

 a larger amount of chlorophyll can be 

 formed ; the stems, indeed, may even become 

 distinctly green. Such an observation as 

 this clearly indicates how closely the forma- 

 tive processes of a plant are bound up with its 

 nutrition. But the extreme readiness with 

 which the dodder responds to an appropriate 

 stimulus, by the production of suckers, is 

 shown by the fact that if one of the stems of 

 the parasite happens to twine round another 

 one, they commonly pierce one another with 

 the suckers which are immediately produced 

 at the places of contact. 



CHAPTER XVII 



COMPOUND ORGANISMS 



IT would be an error to imagine that all 

 the flowering plants in which the production 

 of chlorophyll is arrested are therefore to be 



