44 THEORY OF ORGANIC EVOLUTION. 



stages of evolution, only a few phylogenetic lines, 

 and these only in a general way, may be established, 

 on account of the great incompleteness of the pres- 

 ent plant world. Such a line proceeds from the 

 green filamentous algae through the liverworts to the 

 vascular plants. Among the phanerogams, appar- 

 ently so numerously represented, only phylogenetic 

 series of individual organs can be ascertained, but 

 no phylogenetic series of families. A phylogenetic 

 system of phanerogams is not to be hazarded in the 

 roughest outline. Even the relative rank of the 

 two chief divisions of the angiosperms, the mono- 

 cotyledons and dicotyledons, is a matter of question, 

 as also which family in each of these divisions is to 

 be considered the most perfect. 



