406 TRELEASE— THE DESERT GROUP NOLIXE.E. [April 21, 



Distribution and Origin. 



Like the Yuccese, the Nolineae are all North American, and they 

 are comparably distributed except that none are known from the 

 West Indies. They are among the characteristic plants of the dry 

 temperate backbone of the continent. None extend north of 

 southern Colorado, and no species is known to have a very extended 

 range. Their focal center is evidently the temperate ^Mexican 

 tableland, on which the genera are all represented and to which the 

 majority of their species are confined, Bcaucarnca alone, in its most 

 typical form, being characteristic of the hot country and ranging 

 into Central America. Of the two genera that reach the United 

 States, Nolina only enters into the Californian flora, and that only 

 in the southern desert. Though unrepresented in the intermediate 

 region, from which it may be assumed to have disappeared, this 

 genus also appears in the South Atlantic states, apparently as an 

 ofifset from the grass-leaved Texan stock, rather than indicating its 

 primal home {map). 



The ontogeny of the group is scarcely more than a matter of 

 speculation. No reason is apparent for considering it to be very 

 ancient. Though evidently related to the typically septicidal 

 Yucccc-e, it seems rather more likely to have had a closer evolutionary 

 connection with the typically loculicidal Dracsenese. More satis- 

 factory hypotheses may be held concerning the affinities of the 

 component genera. Nolina may be taken as most closely approach- 

 ing the prototype of the group because of its extensive range, large 

 number of species composing differentiated groups, and conformity 

 to the liliaceous plan in its 3-celled pistil and cotyledonary arch. 

 Calibaiins appears to be an offset of Nolina. Beaucarnca and 

 Dasylirion, with a single-celled pistil, may represent parallel off- 

 shoots from Nolina or a no-longer recognized derivative of that 

 genus ; and the question may be raised whether Bcaucarnca is more 

 than a well-marked subgenus of Dasylirion which, strictly limited, 

 itself consists of two quite dissimilar groups. These affinities may 

 be indicated as follows : ' 



T.T /Calibanus. 



Nolina/ 



\//Beaucarnea. 



^Dasvlirion. 



