32 PLANT LIFE 



however, we can generally distinguish between 

 what is primitively and what is secondarily 

 simple, and all that need be said here about 

 the matter is that in any classification of this 

 sort most people more or less unconsciously 

 adopt an anthropomorphic standpoint and 

 standard. Provided we recognise this for 

 ourselves, we shall avoid confusion of thought, 

 and our mental picture will be the clearer. 



Within the genus Chlamydomonas, which 

 we selected as an example of a primitive 

 plant, we find that some, at any rate, of the 

 species are able to manifest a change of form 

 and character according to the circumstances 

 under which they are growing. This fact 

 will serve as a starting-point from which 

 to trace the development of complication of 

 form and structure in the plant kingdom. 



Individuals belonging to certain species, 

 e. g. Chlamydomonas Braunii, when cultivated 

 on appropriate nutritive media, such as a 

 relatively concentrated solution of mineral 

 salts, or on a damp substratum, cease to 

 multiply in the ordinary way. Instead of 

 the cells which have been formed by the 

 division of a parent-cell becoming separated 

 and swimming away, they remain cohering 

 together. Their cellulose walls swell up and 

 form a gelatinous mass in which, as in a 

 matrix, the cells (i. e. the nucleated proto- 

 plasmic units) which have arisen by the 

 repeated fission of parent cells remain em- 

 bedded. Even the cilia may become en- 



