166 DESCRIPTION OF ASTER; DIVARICATI 
M. V. ps rich woods, I,'89. West ete ne: Au. 
'96, '97, in bud, Au. 1900. REL Mora Valley, in bud A 1900, de- 
layed by drought; x ps Au. 97,'98. Gayhead, Blackwater Knoll, ps 6,'98; 
in bud Au. 26, 190o, delayed by drought. 
12° Jag-edge form. Teeth very close, irregular, some of them 
reflexed. Leaves of heavier, firm texture, more of them oblong- 
acuminate. Late flowering. The most abundant form of the 
species observed in the Potomac region, including plants collected 
Oc. 1—15, 1888, as “A. corymbosus, dentate or jagged-leaf form.” 
13. Aster Parthianus sp. nov. 
Small geniculate plants of rock-faces and clay-banks, with thin 
ovate-lanceolate serrulate deflexed leaves, dark-tipped obtuse 
strongly-ciliate chief bracts, and small terminal inflorescence. 
Name from the sharp back- "ee leaves, suggesting Parthian arrows. 
Fic. 21, plant from Silver Cr., N. Y., Au. 17, '96, in hb. Bz. 
Plants growing outward and then bending dou or some- 
times suberect; some or many of the leaves stiffly deflexed or 
directed backward ; such leaves mostly ovate-lanceolate, strongly 
incurved-acuminate, many of them becoming caudate, finely ser- 
„rulate, with rounded base and short slender petiole. Axiles 
similar, few, gradually reduced. Lower leaves broader, not much 
longer, with rather close sharply acuminate teeth, and with broad 
open sinus. Radicals seen are chiefly elliptic 
Inflorescence a small and irregular loose cluster. Heads 
small or of medium size ; bracts various, in some broad, short and 
truncate, highly ciliate (derivatives direct from typical A. divart- 
catus?), in many others pale, smoothish, more uniform an 
moderately acute (derivatives from A. divaricatus much further 
differentiated, or perhaps blended with other strains of descent. 
In some otherwise similar plants the leaf-form suggests blending 
with A. persaliens, A. stilettiformis, and A. rupicola. Apparently 
conditions of growth, especially those involved in reaching out for 
light and air from crevices of rocks, have caused descendants 
from a number of allied sources to converge into one composite 
group from which many of the differences and traces of descent 
have already disappeared. Most typical plants show the following 
characteristics : 
Stems slender, strong, brownish, flexuous and usually abruptly 
geniculate once or twice at nearly a right angle. Rootstock 
short, thick, curving, its nodes excessively shortened, and long 
continuing enwrapped with petiolar expansions. The whole root- 
