r22 BOTANICAL GAZETTE | FEBRUARY 
ing to the rays of the umbellets then. I have found the carpels 
still adhering to each other as late as October 19. While the two 
plants differ by about two weeks in beginning their anthesis, they 
differ from four to six weeks in the time needed to mature their fruit. 
The fruit of 7. @ureum not only matures more slowly, but also 
adheres more firmly to the carpophores, and requires a greater force 
to detach it. 
This later ripening and firmer attachment of the fruit evidently has 
a bearing on the distribution of the plants. The Zizia is seen scat- 
tered about over wide spaces in localities where it grows, while the 
Thaspium is apt to occur in patches or colonies. The fruit of the 
former is readily torn off by any slight jar given by passing animals or 
by the wind, and is by these means often thrown quite a distance 
around. The fruit ripens and the stalks die before the appearance of 
frost. The fruit of the Thaspium usually falls to the ground with the 
ripened stalk, or this may be cut down by an early frost. Its. firmer 
attachment tends to keep it nearer by when dislodged. The seed is 
from these circumstances left near the parent stock, and from its mode 
of distribution helps to keep the plants in patches. Owing to the 
longer life of the plant the fruit as well as the stem and leaves fre- 
quently become purple in late summer, and quite generally so late in 
the season at the time of frost. 
There is quite a difference in the general appearance of the two 
plants. The leaves of 7. auveum are of a lighter shade of green; their 
texture, even when thin, rather firmer than in Z. aurea, and the network 
with larger and more open meshes. They are bordered by a white 
hyaline line, which often becomes prominent, especially in the lower 
leaves. In Z. aurea the network is very fine, the meshes small, the 
hyaline line very narrow, the whiteness often limited to the tops of the. 
serratures, which are sharp in most cases and callous tipped. Famili- 
arity with this leaf structure enables one to tell the plants in nearly all — 
stages of growth, as. they are quite constant. The flowers of Z. aurea . 
are golden yellow, as its specific name indicates; those of 7. aureum — 
are paler, inclined to a lemon-yellow. _ The rays in the umbels of the | 
latter contract much more on their inner side than those of the former, 
so tnat they bend inward and bring the carpels more into a bunch, and 
make the diameter of the — umbel considerably less than that of 
the umbel when in flower. : 
Two forms of Z. aurea may be noted : (a) A a form, grow- 
