﻿242 MISSOURI BOTANICAL GARDEN. 



the "Macroacanthae" are distinguished from the related 

 fetid-flowered ''Sisalanae" by an oblong-conical rather than 

 urceolate perianth tube, dull seeds, and usually somewhat 

 decurrent horny margin for a short distance below the more 

 grooved terminal spine; and from the more closely related 

 ''Tequilanae" in that this margin is not usually so sharply 

 upturned, and hence limits a less marked quadrate trough 

 next the base of the spine, while the prickles are heavier- 

 based than in either. The three groups, perhaps with the 

 addition of a fourth, *'Miradorenses", are apparently the 

 equivalent of Mr. Baker's "Rigidae" after elimination of its 

 known or presumable Littaea component — the general 

 affinities of which are with his ''Aloideae," notwithstanding 

 a somewhat artificially defined greater firmness of leaf 

 texture. 



The Macroacanthae agree in an open, often flexuously 

 and few-branched at length bulbiferous oblong panicle 

 about as long as the sparsely bracted scape, subsessile 

 not fetid greenish oblong flowers with the filaments inserted 

 between the middle and upper third of the tube in two mostly 

 distinct series, broadly oblong stipitate and beaked capsules 

 with interlacing fibers between their dehiscent valves, and 

 dull heavily and therefore inconspicuously winged seeds. 



In the concise technical treatment which follows, the syn- 

 onymy* is so subdivided as to make possible the application 

 of an appropriate name to possible segregates of either species; 

 but this has been done with the feeling that segregation, to 

 have any real meaning, will need to be effected in the field, 

 rather than on isolated and aberrant garden specimens 

 or on the early descriptions if taken too literally. The real 

 nature and the causation of the multiplicity of forms in .4. 

 macroacantha and the associated very dissimilar but equally 

 multiform A. V erschaffeltii of the Tehuacan region present a 

 clean-cut fundamental problem to capable ecologists. 



* Dealers' catalogues, though occasionally loosely descriptive, are 

 usually bare lists of names; yet they sometimes throw valuable light 



the citation of such catalogues even fuller th^ it^is. ^ 



