22 THE ORCHIDS OF NEW ENGLAND. 
petals shut down so as almost to compel direct approach. 
There is also a little channel along the lip, which,we may 
suppose, catches and guides the proboscis. ‘The insect will, 
therefore, almost invariably touch the rostellum; this will rupt- 
ure, be depressed, and one or both exposed viscid balls stick 
fast “to the intruding body, the viscid matter setting hard, 
and dry, like a cement, in a few minutes’ time. The firmness 
of the attachment is very necessary, for if the pollinia were 
to fall sideways or backwards they could never fertilize the 
flower.” The pollinia would thus be wrenched from their cells, 
and carried away, standing out “like horns ” on the insect’s head, 
eyes, or proboscis. The lip of the rostellum swings back into 
place ‘ when pressure is removed,” so that if but one pollinium 
has been taken, the disc of the remaining one is kept damp and 
in readiness for the next light-winged guest. 
If a pollinium remained erect on the insect, it would strike 
above the stigma of the next flower visited, and fail of its pur- 
pose; but by a curious contraction of the disc-like membrane 
to which its stalk is attached, the pollinium, in about half a min- 
ute’s time, bends downward, “always in one direction, viz., 
toward the apex of the proboscis.” Supposing the insect to 
occupy this amount of time in passing to another plant, “the 
pollinitum will have become so bent that its broad end will 
exactly strike the stigmatic surface of the next blossom,” and 
in case all the pollen is not torn off, enough will be left to fer- 
tilize several other stigmas. In O. mascula (and presumably in 
our own Orchis) the nectar is not “free,” but contained be- 
tween the inner and outer membranes of the spur, and as Mr. 
Darwin explains, “as the viscid matter of the disc sets hard in 
a few minutes when exposed to the air, it is manifest that 
insects must be delayed in sucking the nectar, by having to 
bore through several points of the inner membrane and to suck 
the nectar from the inter-cellular spaces, time being thus 
allowed for the disc to become immovably fixed.” 
