Chap. I. SECKETION OF KECTAB. 43 



show this much intelligence, should persevere in 

 visiting flower after flower of the above-named Orchids, 

 and in keeping their proboscides in constant movement 

 for some time within the nectaries, in the hope of 

 obtaining nectar which is never present? This, as I 

 have said, seems to me utterly incredible. 



It has been shown how numerous and beautiful are 

 the contrivances for the fertilisation of Orchids. We 

 know that it is of the highest importance that the 

 poUinia, when attached to the head or proboscis of an 

 insect, should be fixed symmetrically, so as not to fall 

 either sideways or backwards. We know that in the 

 species as yet described the viscid matter of the disc 

 sets hard in a few minutes when exposed to the air, 

 so that it would be a great advantage to the plant if 

 insects were delayed in sucking the nectar, time being 

 thus allowed for the disc to become immovably affixed. 

 It is manifest that insects must be delayed by having 

 to bore through several points of the inner membrane 

 of the nectary, and to suck the nectar from the inter- 

 cellular spaces ; and we can thus understand why the 

 nectaries of the above-named species of Orchis do not 

 contain free nectar, but secrete it internally between 

 the two membranes. 



The following singular relation supports this view 

 in a striking manner. I have found free nectar within 

 the nectaries of only five British species of Ophrese, 

 namely, in G-ymnadenia conopsea and albida, in 

 Hcibenaria Hfolia and chloraniha, and in Peristylus (or 

 Habenaria) viridis. The first four of these species have 

 the viscid surfaces of the discs of their polHnia naked 

 or not enclosed within pouches, and the viscid matter 

 does not rapidly set hard when exposed to the air, as if 

 it did, it would immediately have been rendered use- 

 less; and this shows that it must differ in chemical 



