OP NAIAS GRAMINEA^ VAR. DELILEI. 57 



XIII. Fertilization. 



The pollination of Naias graminea is entirely effected in 

 the watei'j as there is no provision for an elongation of the 

 peduncle to raise the pistilliferous flowers up to the sur- 

 face of the water, as in Potamogeton Zizii, Valisneria, 

 Anacharis, and other aquatic plants. The structure of the 

 inflorescence forbids its being considered a cleistogamous 

 flower ; whether it is an aquatic type of an anemophilous 

 or an entomophilous plant I cannot determine. 



Some observations I have noted for recording here are 

 of some interest^ as they suggest that pollination is eff'ected 

 in two ways. In the station in which the Naias occurs 

 near Manchester the very slight natural flow of the water 

 in the canal towards the locks is quite sufl&cient for the 

 transport of the pollen, and, though I have not purposely 

 taken any of the canal water to see if it contained free 

 pollen, my home observations leave me no doubt that 

 pollen is carried to the pistilliferous flowers by the cur- 

 rent ; in such case the plant would be hydrophilous. 

 While, however, examining portions of a living plant on 

 which were ripe anthers, I noticed a colony of Vorticellidse 

 attached to one of the fascicles of leaves ; the grace and 

 activity of its movements led me to watch it for a con- 

 siderable time, and whilst so watching it I witnessed grains 

 of pollen whirled in all directions, or drawn into the 

 vortex of the animal by its marginal cilia. The alternate 

 contraction and elongation of the elastic and thread-like 

 pedicles of the colony kept the pollen-grains in constant 

 motion, which left me no doubt that at times the grains 

 would be directly borne to the stigmatoid appendages of 

 the pistilliferous flowers. 



The canal-water is most prolific in animal life ; beetles, 

 molluscs, leeches, rotifers, polyps, larvae of insects, &c,. 



