THE ORCHIDS OF NEW ENGLAND. 59 
the top of the short column, opens in the bud. When the 
flower is fully expanded, the pollen-masses are left quite free, 
supported behind by the anther cells, and lying in front against 
the concave back of the rostellum, with their upper pointed 
ends resting on its crest. Each pollen-mass is almost divided 
into two. The few elastic threads of the grains are weak, and 
' large masses of pollen can be broken off easily. ‘The lip has two 
basal lobes which curve up on each side, and these would com- 
pel an insect to approach the rostellum straight in front. As 
Fic. 16.—LiIsTERA OVATA. (From Muller.) 
1. Side view,of unfertilized flower: ov, ovary. | 
2. Front view, after the pollen-masses, 0, have been removed from the anther. The flat 
‘rostellum (7) is bent forward and partly conceals the stigma (s¢). (Magnified one-half as much 
asi.) #, nectary. 
3. Pollen-masses adhering to a needle (greatly enlarged). c, cement. 
4. Grammoptera leuts, with a number of pollen-masses on its head. 
soon as the flower opens, if the exquisitely sensitive rostellum 
be touched ever so lightly, a large drop of viscid fluid is instan- 
taneously expelled, and, on exposure to the air, in two or three 
seconds the drop sets hard, soon assuming a purplish brownish 
tint. As the pointed tips of the pollen-masses lie on the crest 
of the rostellum, they are always caught by the exploded drop.” 
This drop, then, does the work of a viscid disc for the pollen- 
masses. 
‘When. the anther-cells open, the rostellum slowly curves 
over the stigmatic surface, so that its explosive crest stands at 
a little distance from the summit of the anther; and this is very 
necessary, otherwise the summit would be caught by the viscid 
