INTRODUCTORY 3 



The contrast between the gametophytes of the two groups, 

 especially the female gametophytes, is even greater than that 

 shown by the sporophytes. The male gametophytes of Gymno- 

 sperms when contrasted with those of heterosporous Pterid- 

 ophytes present a much shorter history; and the gametophytic 

 structure produced by the Gymnosperm microspore involves 

 the formation of two or three times as many cells as are formed 

 in the germination of the Angiosperm microspore. The female 

 gametophytes of the two groups, however, are in the main stri- 

 kingly different. As is well known, the female gametophytes 

 of Gymnosperms in general, with their well-organized tissue 

 and archegonia, are almost the exact counterparts of those of 

 Selaginella and Isoetes; while the female gametophyte of An- 

 giosperms remains a morphological puzzle, made still more 

 perplexing by the discovery of the wide-spread phenomenon 

 styled " double fertilization." It is a very significant fact, how- 

 ever, that in spite of the difficulties of the female gametophyte 

 of Angiosperms in the way of interpretation and of origin, it 

 is one of the most remarkably consistent structures known to 

 morphology, the sequence of events in its history representing 

 an almost unvarying schedule, and supplying one of the strong- 

 est arguments in favor of the monophyletic origin of Angio- 

 sperms. 



In view of these and other differences between Angiosperms 

 and Gymnosperms, the question is raised whether we have not 

 been too narrow in the conception of the seed-bearing habit in 

 compelling these two groups to remain as subdivisions of a 

 group Spermatophytes coordinate with Pteridophytes and 

 Bryophytes. In a certain sense, to select a single character, 

 such as seed-bearing, as a basis for the union of two groups 

 otherwise dissimilar is suggestive of artificial classification. 

 Furthermore, to separate the female gametophytes of Gymno- 

 sperms from those of the heterosporous Lycopodiales, and to 

 associate them with those of Angiosperms, is certainly to do 

 violence to a most important suggestion of natural relation- 

 ships. In our judgment, therefore, the designation Sperma- 

 tophytes should be used in a general way, as a term of con- 

 venience rather than of classification, only less extensive in its 

 application than " vascular plants " ; and Gymnosperms and 

 Angiosperms should be recognized as two groups coordinate 



