214 PLANT-LIFE 



tyledons. The Sympetalse are by no means all on the 

 same level of advance, nor must the reader surmise that 

 they all appeared subsequent to the Choripetalse. 

 Many of the latter are highly specialized, and doubtless 

 some forms in both great divisions are to be regarded 

 as contemporaneous. The same may be said in respect 

 to Monocotyledons in relation to Dicotyledons. Forms 

 of various kinds may have arisen from different origins, 

 and have attained high specialization, not in succession, 

 but side by side. It would be foolish to think of floral 

 evolution as following a direct line from lower to higher. 

 It should rather be pictured in the form of a family tree. 

 Just because Orchids are Monocotyledons, they are not 

 to be treated as antedating Daisies, which are Dico- 

 tyledons. Indeed, Orchids are modern, and there are 

 indications that they are not yet at the climax of their 

 evolution. There may have been a period in which 

 some Choripetalse existed as the only Dicotyledons, but 

 it is probable that the higher forms of the Division 

 attained their specialization side by side with the 

 Sympetalae, and that the latter began a successful career 

 upon their own particular lines, so to speak, in early 

 choripetalous times. 



There are two divisions of the Sympetalse. In one 

 the number of petals is equal to that of the carpels — these 

 are the Isocarfce (Gr. isos, equal; carpos, fruit); in the 

 other the carpels are fewer than the petals — these are 

 the Anisocarpw (Gr. anisos, unequal). Separate car- 

 pels are never found in the Sympetalse. They invariably 

 cohere, and form a compound pistil. Following the 

 principle already laid down, we naturally conclude that 

 among the Sympetalse the Isocarpse are more primitive 



