THE AMERICAN NA TURALIST. [Vol. XXXV 1 1 . 



and it seems to me that Professor Bower 1 has effectually 

 refuted the arguments of Dr. Scott, who has been the special 

 champion of the homologous theory in England. More recently 

 Mr. W. H. Lang has reviewed the subject, 2 being more or less 

 non-committal, but rather leaning to the homologous view ; and 

 in this country Professor Coulter < has assumed a somewhat sim- 

 ilar attitude. 



Owing to their perishable nature, the simpler green Algae and 

 Bryophytes have left very meagre fossil remains, so that their 

 geological history is very imperfect, and we are perforce driven 

 to a study of the living forms, as practically our only means of 

 tracing the ancestry of the higher plant forms. Of the vascular 

 plants there are abundant fossil remains which throw much light 

 upon the relationship of the Pteridophytes and seed-plants, and 

 the succession of forms in geologic times, but help but little in 

 determining the lower forms from which the former originated. 



It has been urged that inasmuch as ferns, and even seed- 

 plants, can be traced back to the Devonian, and possibly even 

 further, it is hopeless to expect the secret of the origin of 

 the vascular plants can ever be solved. However, as many 

 extremely primitive forms have undoubtedly survived to the 

 present time, we can learn very much from a comparative study 

 of these with the higher plants, which must have come from 

 forms very similar to them. Of the forms which are of special 

 importance in this connection are the simpler green Algae, and 

 the generalized liverworts. 



Zoologists are in much the same position with regard to the 

 origin of the vertebrates, as botanists are concerning the vascular 

 plants. The former sub-kingdom is certainly as old and probably 



zoologists consider the question of the origin of vertebrates 



I shall not attempt here to discuss the monophyletic ,„- poly- 

 phyletic origin of Pteridophytes, but shall mainly concern myself 

 with the class which at present is the predominant one, the Ferns. 



Nov. 24, Dec. 1, ,898. 

 ' Annals of Botany, 12 : 585-592, 1898. 



