226 A FREE-LIVING -SPOROPHYTE 



the Pteridophytes it is illustrated only within a strictly localised area of 

 affinity. The course of transition from the dependent embryo to the 

 rooted plant, as it is carried out in the individual life, may be held to 

 be the most reasonable guide to the same transition in the past. It is 

 seen to be occasionally through the intermediary of a protocorm, but 

 oftener without. It may be that this indicates correctly the actual course 

 which events took ; and suggests that all vascular sporophytes did not 

 achieve their independence in the same way. 



It is of course possible to take an entirely different view of the 

 relations of the two generations from that here presented, and to consider 

 the dependence of the sporophyte as being itself secondary, and the 

 haploid and diploid phases as having been originally as independent as 

 they are seen to be in Dictyota. In that case the problem would be 

 the converse : viz., to trace the origin of the dependent state of the 

 sporophyte. There is, however, no serious basis of fact or comparison 

 hitherto adduced, which can place this suggestion upon a footing of 

 reasonable probability : it will suffice here to have mentioned that the 

 suggestion has been made. 



