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 

 pollinium 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." 



