Mar., 1911.] The Classification of Plants, 17. 293 



may belong elsewhere. It is believed that the segregation into 

 sub-classes, as given below, is essentailly correct and represents 

 phyletic developments. In the older arrangements the treatment 

 of the series is often very inconsistent, in some cases proceeding 

 from the primitive to the specialized, in others from the most 

 highly specialized to the most primitive, as in the case of the grass 

 family. The arrangement must be inverted beginning with the 

 primitive bamboos and endiiig with such extremely specialized 

 genera as Indian corn. 



The sub-classes at present recognized by the writer are as 

 follows : 



Monocotylae: 



Helobiae. 



Spadiciflorae. 



Glumiflorae. 



Liliifl-orae. 



DiCOTYLAE : 



Thalamiflorae. 



Centrospermae. 



Calyciflorae. 



Amentiferae. 



Myrtiflorae. 



Heteromerae. 



Tubiflorae. 



Inferae. 



There can be little question but that the Helobiae represent 

 the lowest monocotyls and the Thalamiflorae the lowest dicotyls. 

 Any comparative morphology based on phyletic ideas must come 

 to this conclusion. The lower types of these two subclasses are 

 about on a level. There is little point, therefore, to the discus- 

 sions as to whether monocotyls or dicotyls are the higher group. 

 Since the highest dicotyls go far beyond the highest monocotyls in 

 floral specialization, it is more convenient to place the monocotyls 

 flrst in the list, even though the gametophytes of their highest 

 members, the Orchidaceae, probably represent the most extreme 

 reduction and specialization. The classification of the vascular 

 plants should be based primarily upon the sporophyte. 



Finally, it should be clear that generalizations as to primitive 

 conditions and evolutions can not be based upon such extremely 

 specialized forms as Welwitschia (Tumboa), Piperaceae, Casuarina, 

 and other peculiar groups. The gametophytes and the minute 

 morphology have undergone specialization as well as the more 

 exposed parts. 



A general representation of the supposed relationship is given 

 in Figure 1 . The Helobiae begin with the Alismaceae and related 

 forms and end with the Vallisneriaceae which are highly special- 



