652 W. TRELEASE FLORA OF CENTRAL AMERICA 



ters either in the Antilles or in the Gulf region of onr Atlantic States or 

 of Mexico, and passed from the one into the other. Since this is the only 

 yucca with pulpy fruit in our Atlantic region, while baccate species range 

 through Mexico as far as the genus reaches, the probability is that its 

 protot^-pe originated on the mainland to the south, and that in its present 

 form it recrossed into it5 now rather limited areas to the north and west. 

 I^either of these suppositions need be regarded as indicating a land 

 connection between the West Indies and North or Central America, for a 

 plant with edible fruit may have passed easily greater barriers than those 

 separating the TVest Indies from North America. In any event, the 

 Yuccese offer no other indication of such a land connection, and they 

 give no suggestion of a connection between the West Indies and South 

 America. 



Phoeadexdeox axd Fuecr^a SUGGEST Laxd Coxxection with 

 North and South America 



The distinctively American mistletoe genus Phorad-endron possesses a 

 vastly greater American range than either of the groups so far considered. 

 Species are found from ocean to ocean, and from the extreme northwest- 

 ern limits of the United States to the mouth of the river La Plata, in 

 South America. Unlike the other groups, this genus is evidently as much 

 at home in the West Indies as it is on the continent. While the others 

 are preponderatingly, if not exclusively. North American, this genus is 

 almost equally weU represented north and south of the Isthmus; but 

 something like one-third as many species occur in the West Indies as on 

 either continent. It may be, and I think is, older than either genus of 

 Nolineae or of Yucceas and younger than Querent, but no very dependable 

 or direct evidence as to this exists. 



In my study of Ptioradendron,^ I became convinced that two very dis- 

 tinct groups — subgenera, if you like — make up the genus. One of these 

 (the Boreales) includes 23 per cent of the known species; the other 77 

 per cent belong to the other group (Aequatoriales). The significance of 

 the names used for these groups lies in the fact that the first centers in 

 Mexico and the United States, only 2 of its ^Q species reaching Central 

 America and none being found in either the West Indies or South Amer- 

 ica. While none of the Aequatoriales occurs in the United States, over 

 half of them are South American. Of this group more occur in the West 

 Indies than in either Mexico or Central America, though the group is 

 well represented in both of these regions. 



Unlike the oaks, these mistletoes have not passed at all from Florida 



