The Origin of Land Plants 115 



nous tissues in the evolution of the structures of 

 the sporophyte has been particularly emphasized by 

 Professor Bower, who has recently treated this sub- 

 ject at length. (See his recent book, " The Origin 

 of a Land Flora.") 



Of the living ferns there is no question that 

 Ophioglossum approaches more nearly than any 

 other the hypothetical type suggested by comparison 

 with Anthoceros. In this fern the spore-bearing 

 spike (Fig. 12, B) shows very poorly differentiated 

 sporangia, the whole being comparable with some 

 Anthoceros type in which the segregation of the 

 spore-masses was more complete than in the exist- 

 ing species. 



The club-mosses bear the sporangia singly, each 

 sporangium being subtended by a leaf, and these 

 " sporophylls " together often form a cone or 

 " strobilus." In the ferns the leaves are large and 

 the leaves bear, as a rule, very numerous sporangia. 

 Bower thinks that the ferns may also be considered 

 to represent a modification of the strobiloid type, 

 but there are strong objections to be brought against 

 this view. The cone in the horsetails is also of a 

 very different type from that of the club-mosses, 

 and probably is a quite independent development. It 

 seems to the writer that the assumption of an en- 

 tirely separate origin for the type of sporophyte 

 found in the club-mosses and ferns is indicated by 

 the data now available. 



Seed-bearing Ferns. The great importance of 



