INTERPRETATION OF QUERCUS 651 



that it was later than the Pleistocene. Some of Catesby's oak localities 

 have been misunderstood because of the inclusion of both continental and 

 insular species in his illustrations; but it may be said with confidence 

 that Quercus is unrepresented in the West Indian flora except by this 

 single Cuban form. So far as fossil and existing oaks are known^ they 

 offer no facts pointing to a connection of the West Indies with North 

 America in recent time. The absence of such facts may be taken as indi- 

 cating that no such connection has existed. 



NOLINE^ AND YUCCE.I^. INDICATE ABSENCE OF CONTINENTAL LaND 



Connection 



Among the xerophytic lily-like plants I may claim sufficient familiarity 

 with the liliaceous groups Nolinese and Yuccese and the Amaryllidaceous 

 group Agave^e to discuss their bearing on this question. Unlike the oaks, 

 these are all exclusively American ; and they appear to be of late Tertiary 

 origin, though ^^ery little is known of them except as more recent plants. 



The Nolineae^ are not known to occur away from continental North 

 America. They range from southern Colorado southwestward through 

 Baja California and southeastward over the tableland, one of their four 

 genera (Beaucarnea) dropping into the tierra caliente of Vera Cruz, 

 Yucatan, and Chiapas in Mexico and the lower mountains of Guatemala. 

 An eastern extension of another (Nolina) is known for South Carolina, 

 Georgia, and Florida through evident derivatives of its Texan representa- 

 tives, though it is absent from the intervening Gulf States. This group 

 of the tableland, therefore, throws no light on the question, unless, nega- 

 tively, the absence of its representatives from the West Indies indicates 

 that Cuba has been connected with neither Yucatan nor Florida since the 

 appearance of Beaucarnea in the former and of Nolina in the latter. 



The Yucceae, also absent from South America, appear to be more dis- 

 tinctly boreal plants than the Nolinese are. They range southward 

 from the great bend of the Missouri River to the Atlantic and Pacific 

 coasts, and, over the tableland, to Puebla and Jalisco. In the West Indies 

 only one representative of this group is known, the common Spanish 

 dagger of our Gulf States. This is fairly wide-spread through the islands, 

 but perhaps never free from question as to spontaneity, because it is 

 planted everywhere.* In its genus, this species {Yucca aloifolia) is dis- 

 tinct in lacking a papery core to its fleshy fruit and in having acquired 

 or retained a power of self-pollination which its cougeners do not possess. 



If these differcMicos arc significant, and iC the Sjiauisli dagger is native 

 to the islands, it may be that this species acquired its distinctive charac- 



