44 THE ORCHIDS OF NEW ENGLAND. 
is, on that account, easily overlooked in the woods, but “it 
| serves,” says Professor Gray, “almost completely to exemplify 
Mr. Darwin’s account of the mechanism of Perestylus viridis.” 
The latter authority informs us that the widely separated discs 
have oval balls of viscid matter on the under side, and that 
“the upper membrane to which the stem of the pollinium is 
attached is of large size relatively to the whole disc, and is 
freely exposed to the air. Hence probably it is that the pol- 
linia, when removed from their cases, do not become depressed 
until twenty or thirty minutes have elapsed. Supposing a pol- 
linium to be attached to the head of an insect and to have 
become depressed, it will stand at the proper angle vertically 
for striking the stigma. But from the lateral position of the 
anther-cells, notwithstanding that they converge a little toward 
their upper ends, it is difficult to see at first how the pollinia 
when removed are afterward placed on the stigma; for this is 
of small size and is situated in the middle of the flower be- 
tween the two widely separated discs.” 
a He explains as follows: The base of the 
elongated lip forms a rather deep hollow 
in front of the stigma, and in this hollow, 
but some way in advance of the stigma, a 
minute slit-like orifice leads into the nec- 
Fic. 11.—A. Peristvius viei- tary. Hence an insect in order to suck the 
pis. (From Darwin.) 
a, anther-cell ; 2, entrance 
to nectary ; 2’ xz’, nectar se- ; : . . 
chine sodas ¥ igen front of the stigma. The lip has a ridge 
nectar would have to bend down its head 
passat Tip. down the middle, “ which would probably 
B. H. viripis, VAR. BRAC- ; A 
TEATA. induce an insect first to alight on ‘either 
side; but apparently to make sure of this, besides the true — 
nectary, there are two spots which secrete drops of nectar on 
each side at the base of the lip, directly under the two pouches. 
An insect alighting “on one side of the lip so as first to lick up 
the exposed drop of nectar there, from the position of the 
pouch exactly over the drop, would almost certainly’ detach 
