3 oo BOTANY OF THE LIVING PLANT 



to trace the probable origin of many of those features which charac- 

 terise organisms higher in the scale. For instance, by comparison 

 of members of more than one natural sequence of living organisms, 

 the suggestion is clearly given how differentiation of sex arose. This 

 is only one instance of those illuminating consequences which follow 

 from the comparative study of organisms lower in the scale with 

 those which are more advanced. It is in fact upon the cumulative 

 effect of such comparisons that it has been found possible to base a 

 rational theory of Descent, applicable to Organic Life as a whole. 



Towards the end of the last century Klebs called attention to the 

 affinity between the Flagellata and the Algae : the view now generally 

 held is that the old distinction between the two cannot be maintained. 

 Indeed, from the botanical standpoint, it has been suggested that the 

 term Flagellata should be discarded. The most primitive group of 

 plants, the Protophyta, would then include both the flagellate and 

 algal types of organisation, such characteristics as motility, the 

 possession of a cell wall and sexual reproduction, having appeared 

 at different stages in the evolution of the different Classes of this large 

 and varied group. 



