§74 EEVIEWS. 



visited ; but they do not retain this position, they gradually become 

 depressed and point forwards, and assume such a position that they 

 infallibly strike the stigma of the next flower visited. The viscid 

 stigmatic surface is not adhesive enough to overcome the attachment 

 of the whole poUinium to the insect's head, but is adhesive enough to 

 overcome the cohesion of the pollen grains, inter se, which are conse- 

 quently detached in masses, and one poDinium may therefore fertilize 

 many flowers. There are many other beautiful little contrivances 

 noticed by Mr. Darwin which are brought into play in this operation, 

 of which we have given an outline only. 



Orchis pyramidalis difiers considerably from its allies ; the most 

 cmious point connected with it being the union of the viscid balls of 

 the pollinia into the form of a siugle saddle-shaped disc, which clasps 

 the autennse of moths in a most rapid and remarkable manner, causing 

 a divergence of the pollinia : but for this divergence, and their suc- 

 ceeding depression, they could not reach the stigmatic sm'faces of 

 subsequently visited flowers. O. ustulata presents many points in 

 common with O. pyramidalis. A catalogue is given of twenty-three 

 sdecios of Lepidoptera which were fovmd to have pollinia of O. pyra- 

 midalis attached to their probosces, one of which bore seven pair. 



Oplirys mwscifera. In this plant the pollinia have doubly-bent 

 caudicles, the eflect of which seems to be the same as that of the 

 movement of depression in Orchis. 



Ophrys aranifera. The caudicles here are nearly straight, and a 

 movement of depression is hence necessitated. 



In O. apifera the method of fertilization differs, not only from all 

 others of its genus, but from all other Orchids. The greatest structural 

 difference is in the caudicles, which are so slender as to be flexible 

 with the weight of the poUen itself. The consequence is, that the pol- 

 linia hang out of their pouches, and are blown by the wind against 

 the stigmatic surface, and self-impregnation ensues almost infalUhly. 

 Mr. Darwin finds it almost impossible to escape the conclusion that 

 self-fecundation is here absolute : his discussion of the case is most 

 ingenious, but he can do no more than show that crossing is 

 possible. 



O. arachnites. The priucipal point established regarding this is, 

 that it is certainly not, as supposed by some, a variety of O. apifera, 

 but more closely allied to O. aranifera, with which it agrees in its 

 method of fecundation. 



Herminium Monorchis has floAvers highly attractive to bisects, and 

 seems adapted to a similar mode of fertilization as Orchis. 



Hahenaria viridis. There is no movement of depression in the 

 -pollinia, and it is not apparent at first how the latter can strike the 

 stigma. The explanation is most curious and unique. There are 

 three nectarial spots, and an insect bearing the pollen must, to reach 

 the two lateral of these, so move its head that the pollinia strike tlie 

 stigmata ; the supplementary nectaries thus replacing the power of 

 movement of the caudicles and disc. 



