84 MORPHOLOGICAL DEVELOPMENT. 



question after what manner the integration took place, thei 

 is an hypothesis which renders it comprehensible, and agrees 

 both with the structures of the two kinds of shoots and the 

 structures of the two kinds of seeds, as well as with various 

 of the other phenomena the two types present, it has strong 

 claims for acceptance. 



Eeconsideration suggests the following remarks. 



1. Alternation of generations is a means of furthering 

 multiplication. To be effective each member of either genera- 

 tion must be a self-supporting centre of growth or diffusion 

 or both. Hence if, as in the Liverworts, one of the so-called 

 alternating generations is not independent, but a permanent 

 growth on the other — a parasite — it is a misuse of words 

 to call the arrangement Alternation of generations. (Since 

 this was written I have found that Sir Edward Fry takes the 

 same view. He approvingly quotes Professor Bower, who 

 says that " the alternation of generations is not an accurate 

 statement of facts or a useful analogy.") 



2. The alternating of sexual and non-sexual processes is 

 not fundamentally distinctive; for, as shown by sundry 

 Archegoniates, it is an inconstant trait, and as shown by 

 Klebe' experiments on Vaucheria, the conditions may be 

 varied so as to determine its occurrence or non-occurrence. 

 Nay, the same individual may reproduce in either way. 



3. Still more significant is the fact that in some of the 

 marine Thallophytes, there is a process like that which in a 

 moss or a fern is considered an alternation of generations, 

 whereas in others, as the Brown Wrack (Fucus), each genera- 

 tion is sexual. Thus the presence or absence of this mode of 

 genesis cannot be a cardinal distinction. 



4. With these facts before us, it is not only a reasonable 

 supposition but a highly probable supposition, that there have 

 existed plants of the Liverwort type in which the so-called 

 alternation of generations did not take place. If so, nearly all 

 the foregoing objections to my hypothesis fall to the ground.] 



