520 TUBEROUS ROOTS OF THE ORCHIDE.E. 



mentary ; and in some other species, all three are occasionally 

 present as complete stamens. 



695. There is much difficulty in understanding how the usual 

 influence of the pollen on the stigma can be effected in these 

 plants ; since the pollen is not capable of being scattered as a fine 

 powder through the air, as in other plants ; and if it were to fall 

 out in a mass, it would hardly touch the stigma. Some have 

 supposed that absolute contact of the pollen with the stigma is 

 not necessary, and have thought that the fertilising influence 

 could be communicated through the stalk of the pollen-mass. But 

 this is now proved to be incorrect; as numerous experiments 

 have shown that the contact is as necessary here as in other 

 plants. It is difficult to perceive, however, in what manner it 

 is naturally effected ; and recourse has even been had to the sup- 

 position, that the agency of insects is necessary, in order to drag 

 the pollen-masses from their case, and to diffuse their granules 

 over the stigma. 



696. On turning our attention to the general aspect of either 

 of our commoner British orchises, we observe that it has a fleshy 

 root usually consisting of two oval tubers, and of a number of 

 succulent fibres ; that its leaves, which have the simple- veined 

 structure characteristic of Monocotyledons, spread upon the sur- 

 face of the ground ; and that a straight flower-stalk is shot up 

 from the midst of these. The stem and roots are connected with 

 but one of the tubers ; the other arises as a sort of lateral bud 

 from this one. When the stem has unfolded its flowers and 

 ripened its fruit, it dies down to the ground, and is succeeded in 

 the ensuing season by a stem developed from the second tuber, 

 the first being exhausted. This, again, serves for the vegetation 

 of one season only, and a new tuber is formed as a bud, from 

 which the next year's stem will be developed. Hence the species 

 possessing this kind of root, always have a pair of tubercles, one 

 shrivelling and in process of exhaustion, the other swelling and 

 in process of completion. Sometimes the bottom of the stem, 

 instead of forming a new tuber upon its side, pushes out a slender 

 subterranean root-like runner, which, after growing to some 



