44 OPHKE^. Chap. I 



nature from that in the foregoing species of Orchis. 

 But to make sure of this fact I removed the pollinia 

 from their anther-cells, so that the upper as well as the 

 under surfaces of the viscid discs were freely exposed 

 to the air ; in Gymnadenia conojysea the disc remained 

 sticky for two hours, and in Habenaria chlorantlia for 

 more than twenty-four hours. In Peristylus viridis the 

 viscid disc is covered by a pouch-formed membrane, 

 but this is so minute that botanists have overlooked 

 it. I did not, when examining this species, see the 

 importance of ascertaining exactly how soon the 

 viscid matter set hard ; but I copy from my notes 

 the words written at the time : " disc remains sticky 

 for some time when removed from its little pouch." 



Now the meaning of these facts is clear : as the 

 viscid matter of the discs of these five latter species is 

 so adhesive that it serves to attach the pollinia firmly 

 to the insects which visit the flowers, without setting 

 hard, there would be no use in the insects being 

 delayed by having to bore holes at several points 

 through the inner membrane of the nectaries ; and in 

 these five species, and in these alone, we find copious 

 nectar ready stored for rapid suction in open nectaries. 

 On the other hand, whenever the viscid matter sets 

 hard by exposure for a short time to the air, it would 

 manifestly be advantageous to the plant, if insects 

 were delayed in obtaining the nectar ; and in all such 

 species the nectar is lodged within intercellular spaces, 

 so that it can be obtained only by the inner mem- 

 brane being penetrated at several points, and this will 

 require time. If this double relation is accidental, 

 it is a fortunate accident for the plants ; but I cannot 

 believe it to be so, and it appears to me one of the 

 most wonderful cases of adaptation which has ever 

 been recorded. 



