36 VARIATION IN ASTER 
put forth a very few larger heads instead of numerous smaller ones. 
Sometimes the central head of one of the Dévaricati shows a 
similar excessive size; and sometimes the terminal head of each 
branch, as compared with the subsequent lateral heads. Some- 
times this excess of size is merely apparent and proves on exam- 
ination to be merely excess in number of rays. In either case 
the first localization of the growth-impulse has had first and best 
opportunity to absorb and make over the unfabricated plant 
material into flowers. 
SINUS-CHARACTERS 
Other characters which are tolerably constant within the species, 
when due allowance is made for development stages, are to be 
drawn from the leaf-form and especially its relation to cordation. 
Leaf-form, while at first seeming so variable as to be wholly 
baffling, proves within certain limits for each species (indicated 
with each description) to have great value as a distinction ; and it 
possesses the special merit of being evident, and of giving to the 
plant much of its characteristic general aspect. In cultivation it 
does not alter as quickly as many other characters; size, for 
example. 
Sinus-character is the most important single feature of the leaf- 
form. Sinus-characters are rather constant, but require very 
cautious application from the transitions which a normal stem 
develops, as the sinus is gradually or suddenly obliterated among 
the upper leaves. Taking the best-developed sinus from among 
basal cauline and radical leaves as the type for the species, we get 
such results as these : 
Sharp deep sinus, A. carmesinus. 
Sharp shallow sinus, merely a notch, A. flexilis. 
Narrow deep sinus, A. orbicularis. 
Broad deep sinus, A. macrophyllus. 
Broad shallow sinus, A. zanthinus. 
Brace-sinus, or tricurve-sinus, such as the last but with the 
center decurrent a little down the petiole, the entire sinus forming 
the outline of a printer’s brace; a very frequent type, especially 
characteristic of A. arcifolius and A. violaris. 
Excavated sinus, one narrow at its entrance but enlarged cir- 
cularly within; A. excavatus. 
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