322 COMPOSITE. Aster. 



1. Biennials, rarely annuals or perennials, with leaves disposed to be incised or pin- 

 natifid : scales of the involucre with green tips : rays sometimes sterile : akenes 

 with strong marginal ribs and some slender nerves on both faces. (Involucre 

 commonly resembling that of Corethrogyne.} MACELERANTHERA. (Maclice- 

 ranthera, Nees. Dieteria, Nutt.) 



* Rays styliferous, but sometimes infertile. 



1. A. tanacetifolius, HBK. Biennial or annual, pubescent and somewhat 

 viscid, a foot or less high : leaves once to thrice pinna-tind, the lobes small and nar- 

 row : heads large, loosely corymbose : scales of the hemispherical involucre linear 

 and with spreading herbaceous tips : rays 20 or more, violet : akenes villous. 

 Machceranthera tanacetifolia, Nees ; Hook. Bot. Mag. t. 4624. Dieteria coronopi- 

 folia, Nutt. in Trans. Am. Phil. Soc. n. ser. vii. 301. 



S. E. California, on the east side of Providence Mountains, Dr. Cooper ; thence through Ari- 

 zona to Colorado, east of the Rocky Mountains, and into Mexico. 



A. (MACH^ERANTHERA) PARVIFLORUS, Gray, which occurs on the Gila in Arizona, and may be 

 found within the State, is smoother and much smaller. 



2. A. incanus, Gray. Hoary with a fine and close soft pubescence, slightly if 

 at all viscid, a foot or two high, loosely branched : leaves linear or narrowly lanceo- 

 late, entire, or some with a few lateral teeth, acute (an inch or so in length, about 

 2 lines wide) : heads solitary terminating the branches, large : scales of the hemi- 

 spherical involucre linear-lanceolate, with long and squarrose-spreading or reflexed 

 foliaceous tips : rays 30 or more, violet : akenes canescent. Diplopappus in- 

 canus, Lindl. Bot. Reg. t. 1693 ; Hook. Bot. Mag. t. 3382. Dieteria incana, Torr. 

 & Gray, Fl. ii. 100. 



California, raised in England from seed collected by Douglas ; the station unknown. Speci- 

 mens which accord with it were gathered in Guadalupe Canon, Sonora, by Capt. E. K. Smith. 

 Head over half an inch in diameter across the disk : rays two thirds of an inch long. 



3. A. canescens, Pursh. Biennial, minutely puberulent-hoary or often green, 

 a foot or so in height : stems rigid, corymbosely or paniculately branched above : 

 leaves varying from oblong-lanceolate or the lowest spatulate to linear, incisely or 

 almost spinulosely toothed, or sometimes entire, those of the flowering branches 

 reduced to subulate bracts : heads few or numerous, solitary, or mostly corymbose 

 or panicled : scales of the campanulate or obconical involucre rigid, appressed, 

 with short more or less squarrose-spreading green tips, the outer successively 

 shorter : rays 20 to 30, violet or bluish-purple : akenes canescently-pubescent. 

 A. biennis, Nutt. Gen. ii. 155. Dieteria canescens, pulverulenta, divaricata, viscosa, 

 & sessiliflora, Nutt. in Trans. Am. Phil. Soc. 1. c. Machceranthera canescens, Gray, 

 1. c. ; Eaton in Bot. King. 



Dry regions, in the mountains behind San Diego and on the eastern slope of the Sierra Nevada 

 (Mono and Tahoe Lakes, &c.), extending north to the British boundary, and east to the eastern 

 base of the Rocky Mountains : a characteristic and most variable species of the region. Heads 

 in the larger forms half an inch in diameter, and the rays half an inch long ; in others barely half 

 that size, and the flowers much fewer. It is useless to "distinguish particular varieties. Only low 

 and small-headed forms have as yet been found in California. 



* * Rays completely neutral. HESPERASTRUM, Gray. 



4. A. Shastensis, Gray. Dwarf from a perennial rootstock, branched and 

 tufted from the base, a span high, puberulent-hoary : leaves small, spatulate or ob- 

 long, entire : heads solitary terminating the branches, small : scales of the campanu- 

 late involucre lanceolate, somewhat hoary and viscid, the outer with loose green 

 tips, the inner nearly destitute of herbaceous tips : rays 15 to 20, rose- violet. 

 Machceranthera (Hesperastrum) Shastensis, Gray, Proc. Am. Acad. vi. 539. 



On Mount Shasta, at about 9,000 feet, Brewer. Resembles a dwarf state of the last. Involu- 

 cre 4 lines long : rays 3 lines. 



