MUSCULAR SYSTEM. 98 



I will take one more illustration from a very different 

 part of the organized kingdom. 



In most of the Orchids, as Mr. Darwin has shown 

 us in his excellent work on that order of plants, the 

 pollen from one flower is carried by insects to another ; 

 and if this is not done, the flower is not fertilized and 

 the seed is not developed. Now, in our small Orchids, 

 when an insect lights on the flower the sticky end of 

 the pollinium adheres to the insect, and is thus carried 

 away ; in some of the large tropical Orchids, however, 

 the part of the flower which insects visit is so far from 

 the pollen-masses that a different arrangement is neces- 

 sary. In Catasetmn, for instance, there is a long 

 sensitive process, or antenna, which hangs over the 

 part on which insects alight, in such a manner that 

 they can scarcely fail to touch it. Directly they do so, 

 the flower throws its pollen-masses in the direction of 

 the insect, and with such force that they will fly two or 

 three feet. J have myself seen a flower, when its 

 antenna was touched, throw the pollen-masses for 

 about two feet, across a small table and to a window, 

 on which they stuck. 



This is not eff'ected by muscular action ; but the 

 stalk on which the pollen-masses stand is bent round 

 a protuberance, and held in position by a delicate 

 membrane. When the sensitive antenna is touched this 

 membrane gives way, and the elasticity of the pollen- 

 stalk throws it forwards with much force, as just 

 described. 



The arrangement of the muscles of the ventral 

 tube (Pis. LYII and LVIII) are extremely remark- 

 able. 



It is evident that the protrusion of the two filaments 

 which can be projected from the end of the tube, as de- 

 scribed in pp. 68, 69, could not be effected by muscular 

 influence, excepting, indeed, by the indirect effect of 

 those muscles which contract the cavity of the body, 

 and thus, intensifying the general pressure, squeeze 

 out, as it were, the two filaments. 



