40 VARIATION IN ASTER 
the more usual wings are irregular as in A. divaricatus alatus, and 
scarcely reducible to definite forms. Wings seldom occur on all 
the leaves at once, or on the lower leaves; and the chance of their 
occurrence is more and more probable upward. In fact the same 
plant of either A. macrophyllus or A. divaricatus often shows all 
the transitions in petiole-formation, from a sessile to a slender 
petioled leaf, that are so remarkably manifested in A. undulatus. 
BRACT-CHARACTERS 
Bracts form one of the most helpful sources for discrimi- 
nation of species after making due allowance for a certain range 
of change which is to be expected. Characters may be drawn 
from their number of rows or ranks, an optical effect due to over- 
lapping, or to such successively increased height of inner bracts 
as to produce the appearance of 5 ranks in A. biformis and some 
other Biotian species. The other extreme, a single rank of bracts, 
is produced when the outer, middle and inner ones are substan- 
tially alike in length, as often in A. puniceus, A. INovi- Belgii, etc. 
Triseriate appearance of bracts characterizes most of the glandu- 
lar Biotian species, with the outer lowermost bracts broad-based, 
and narrowed to an acutish but dark conspicuous point, as in A. 
macrophyllus ; the tips of the second and third rows equally dark 
and conspicuous ; those of the fourth narrow, pale and unobserv- 
able ; few of the fifth now developed at all. 
Quincunx pattern, with dark tips above the spaces below. The 
dark tips of the 3 rows may make a bright conspicuous quincunx 
or chequered pattern, usually among kindred of A. /aevis, A. cor- 
difolius, A. undulatus, A. divaricatus and A. macrophyllus. Other 
kindred species may have the bract-tips so little darkened as to 
leave the involucre pale or nearly a monotone in color; as A. 
curvescens, A. olivaceus, A. sagittifolius. 
Scarious margins, wide and shell-pink or, later, colorless, in A. 
fragrans, narrow in A. divaricatus, purple in A. biformis, and some 
other species, are apt to be quite persistent through a species and 
to be best developed on the middle bracts ; 7. e., excluding the lower- 
most, which are seldom scarious-edged, and excluding the inner- 
most, which are likely to be quite scarious in most species. 
Ciliation of bract margins also forms a rather persistent spe- 
