82 
THE AMERICAN BOTANIST. 
I have noticed that the3^ so dispose their leaves as to face 
the sun, especialh* in the afternoon, the upper side alwa3^s 
being turned towards it. It is odd to see plants all facing 
one way in this manner and suggests the familiar action 
oi Silphium laciniatum and Lactvca scarioJa, both known 
as ''compass-plants." I have never seen the trick recorded 
of Cassia. Another feature of the leaves has struck me, 
viz : — their very close imitation, when closed, of theloment- 
like pods. Is this a protective disguise lor some reason ? 
'The pods are not actual loments as the\^ split their whole 
length, but thev are deeph^ indented b^- each seed. 
Another plant, verv common on arid plains and along 
our sea-beaches, is Strophostylis or wild bean. The 
flowers, though small, are pretty and of a peculiar shell- 
like pink. The idea of the shell is still further suggested 
b^^ the peculiar twist of w^mgs and keel. Gra^^ gives this 
curious account of their cross-pollination b\^ insects, "The 
keel, inclosing the stamens and pistils, is prolonged into 
a narrow snout which is spirally twisted; the stigma is 
oblique on the tip of the style, and the beard on the st^de 
is mainly on the same side that the stigma is; the wing- 
petals stand forward and turn downward, forming a 
convenient landing-place for bees. The anthers early 
discharge their pollen, much of which adheres lightly to 
the base of the style. In the untouched flower all, from 
first to last, is concealed in the coiled keel. Press down 
the wing-petals, and first the stigma and then the pollen- 
laden tip of the st3de projects from the orifice ; remove the 
pressure and they withdraw within. When this pressure 
is made by a bee resting on the wing-petals, while search- 
ing for nectar within the base of the blossom between the 
keel and the standard, the same movement occurs." Of 
course the insect is then dusted by the pollen which he 
bears aw^ay to another flower. 
Apios tuberosa, the w^ell-knowm "ground-nut," has 
also an extraordinary contrivance for cross-pollination 
w^hich may be found described in Vol. I of Gray's "Struc- 
tural Botan^^" The flowers are of a peculiar minghng of 
