36 The Botanical Gazette. (January, 
of service in evading more or less the full effect of the sun's 
rays during the hottest part of the day. This is true even of 
more advantageous than a horizontal position would be. 
The same result is secured in other plants by simply as 
suming an erect position. Aform of Linum Virginianum L. 
is an interesting variation of this habit. Here the leaves are 
toward the right and toward the left. The lower side of the 
leaves is thus exposed and the upper side more or less pro- 
tected. In its earlier history the plant must have been simply 
a case of vertical leaves. Aster adnatus Nutt. must also a 
one time have had leaves entirely free from the stem, but 
erect, and more or less appressed to the same. In that po 
sition the lower half of the midrib became adnate to the 
stem and since then the upper half of the leaf has again re- 
sumed a tendency to spread. - 
It is Aster concolor L., however, which is the most intet 
esting of the latter class of plants. Here the upper leaves are 
erect, appressed to the stem, and rather crowded. 1% 
so erect, but have rather an ascending position. They het 
also show a very marked tendency to place their vertical lea 
blades in a north and south plane. This tendency disappeats, 
or rather, is obscured among the more crowded and ef on 
upper leaves. Where exposed to the sun freely the north 
mention. A number of years ago, the writer, I think, 
dence of a tendency to evade the hottest and most direct 
of the sun. 
