26(25). Leaves of midstem with slight basal auricles which make it appear as if 

 the leaves clasp the stem more than half the circumference though 

 the scar involves only about half 19. A. scabricaulis. 



26. Leaf scar commonly involving as much as half the circumference of the 



stem but leaf auricles absent (27) 



27(26). Mature disk corolla (that is, corolla from a floret with anthers exserted 

 or beginning to be exserted) 3-3.5 (-3.9) mm. long, consisting 

 of a tube 1-1.5 mm. long plus a throat 0.8-1.2 (-1.4) mm. long, 

 plus lobes 0.7-1 (-1.2) mm. long 14. A. lateriflorus. 



27. Mature disk corolla 4-6 mm. long, consisting of a tube 1.3-2.5 mm. long 



plus a throat 1.5-3 mm. long, plus lobes 0.5-1.1 mm. long (28) 



28(27). Phyllaries relatively weakly graduated, the shortest outer ones about 

 half as long as the longest inner ones 17. A. praealtus. 



28. Phyllaries relatively strongly graduated, the shortest outer ones about a third 



as long as the longest inner ones (29) 



29(28). Mature disk corolla 5-5.6 mm. long, with lobes 0.7-1 mm. long plus 

 throat 2.4-2.7 mm. long, plus tube 2.2-2.5 mm. long; in Trans- 

 Pecos Texas 7. A. hesperius. 



29. Mature disk corolla (4.1-) 4.5-5 mm. long, with lobes 0.5-0.9 mm. long 



plus throat 1.5-2.5 mm. long, plus tube 1.3-2.2 mm. long; in 

 eastern half of Texas 20. A. Eulae. 



1. Aster spinosus Benth. Mexican devil-weed. 



Colonial by rhizomes, essentially leafless or producing a few small leaves when 

 injured near the ground, with minute subulate leaves scattered in some stems; 

 axillary branches often transformed into thorns; heads as in A. subulatus (rays 

 short as in van euroauster) but the phyllaries more strongly graduated and the 

 pale narrow margins narrower than the median dark stripe. Leucosyris spinosa 

 (Benth.) Greene. 



Locally very abundant on roadsides and other weedy slopes and banks, about 

 streams and irrigation canals, in river beds, seepage areas and edge of water in 

 marsh, in Okla. (Payne Co., southw.) and s. and w. half of Tex., uncommon 

 n.e. to Brazos, Robertson and McLennan cos., N. M. (Dona Ana Co.) and Ariz. 

 (Coconino and Mohave, s. to Cochise, Pima and Yuma cos.), summer-fall; C.R. 

 n. and w. to Calif., Ut., Ariz., N.M., Okla. and Tex. 



2. Aster tenuifolius L. Fig. 749. 



Relatively low turgid-succulent perennial; rhizomes apparently creeping in mud; 

 leaves only about 2 mm. broad, to 1 dm. long; heads larger (but fewer) than in 

 A. subulatus and A. spinosus (see below) but with most of the same characters; 

 each plant or shoot from the rhizome with usually only about 10 to 20 remote 

 heads. 



Infrequent, salt marshes or brackish mud, s.e. Tex. (Aransas, Brazoria, Calhoun 

 and Galveston cos.), June-Nov.; coastal areas n.e. as far as L.L and N.H. 



3. Aster subulatus Michx. Hierba del marrano. Fig. 750. 



Robust much-branched glabrous annual; leaves linear-subulate, rarely serrate, 

 mostly 1-10 (-20) cm. long, 2-4 (-7) mm. broad, much-reduced toward the top 

 of the plant; involucres turbinate, of a few series of linear phyllaries, each phyllary 

 pale but with a darker linear midrib (if laterally expanded then the widest portion 

 no more than twice as wide as the narrowest). 



In shallow water of ditches and pools, wet mud flats, marshes and floodplains 

 and in coastal saline marshes, in Okla. (Love and Stephens cos.), throughout Tex., 

 N.M. and Ariz. 



1618 



