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 Peristylus 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." 



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- 

 Fig. n.-A. Peristylus viri- tary. Hence an insect in order to suck the 



Dis. (From Darwin.) 111 



a, anther-ceii; », entrance nectar would have to bend down its head 



cressets*' *,' stigma • '" il! h ° nt ° f tHe sti g ma - The H P haS a rid g e 



part of lip. down the middle, "which would probably 



B. H. VIRID1S, VAK. BRAC- * J 



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 



