1909] WIELAND—WILLIAMSONIAS OF MIXTECA ALTA 435 
tion from such a primitive, or archaeo-amarillidaceous plant would 
consist in basi-lateral fusion of the sporophylls and development 
of a trilocular ovary, with the synchronous reduction and change of 
the microspore zone to the series of six interiorly borne stamens, after 
the manner shown to be feasible in the above series A’, Aj. Such 
Wwe conceive to have been the origin of the yuccas and agaves; for 
it is no more improbable that heterospory should in many primitive 
stocks arise thus regularly in each of an apical whorl of sporophylls, 
than that it should find expression in the 
Segregation of a basal group of megasporo- 
phylls followed by an apical group of micro- 
Sporophylls, as in Cycadeoidea. 
Evidently in Agave americana the last 
Stage of fusion resulted in the suppression 
of the basal or megaspore region of three 
alternate fronds. Nor is it so difficult to 
conceive how, the plant finding the inclosure 
of the ovarian region to its advantage, an 
elongation of the style finally resulted, with 
the retention of the gametophytes and seeds. 
Also, the long filaments must have been . 
very readily produced by the flower under 
the stress of impulses that had to do with } 
nothing else than the ordinary phenomena of fertilization. Such, 
Surely, are the conclusions one may reach from the macroscopic 
Xamination of flowers like Agave and perchance likewise of the 
Tose hip. 
While the manner of evolution just outlined is in reality not 
utterly different from that of the Magnoliaceae, the order in which 
the parts are segregated clearly indicates a remote separation of the 
several stocks involved, and therefore the virtual polyphyletic origin 
of the angiosperms. But of course, when the initial changes, and 
When the major or crucial changes leading up to the two groups now 
Considered so briefly, took place, and which group is in reality the 
More ancient, are questions that only the future may answer. 
Having seen that the ovulate region, whether locular or strobilar, 
and whether there are few or many ovules, offers no impassable 
