ON NA1AS GBAMINEA DEL., VAB. DELILEI . MAGNUS. 



19 



This divergence of form in the pollen-grain of Naias major 

 suggests at first sight inaccuracy of observation, but I have found 

 both globose and elongate pollen in the anthers of the Lancashire 

 Naias graminea. The globular form is represented in fig. 79, and 

 the elliptical form is given in fig. 80, both drawn to the same scale. 



Fia. 80. 



Undoubtedly the pollen is globular in its early stages, but, after 

 selecting what appeared to be perfectly mature anthers just at the 

 period of dehiscence, the pollen which emerged was found to be 

 globose, as drawn, in one anther, and elliptico-cylindrical in another 

 anther. Whether the globose pollen ultimately passes' into the 

 elliptical form, and that the latter represents the mature pollen, or 

 whether there is a dimorphism in the pollen-grain, I cannot 

 pronounce ; I can only certify to the occurrence of both forms in 

 plants from the same station, and that the globose form is much 

 the rarer of the two. 



In its fresh state the pollen-grain is of a pale yellow colour, and 

 its contents are granular. It must be produced in great abundance, 

 as I have frequently found it in a free state in the water of the 

 glass jars which have held the living plant during these investi- 

 gations ; grains also occur floating about in the chloride of sodium 

 solution, which I use for mounting the dissections of the plant for 

 permanent microscopic examination. 



XIII. — Fertilization. 



The pollination of Naias graminea is entirely effected in the 

 water, as there is no provision for an elongation of the peduncle to 

 raise the pistilliferous flowers up to the surface 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 anemo- 

 philous 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 effected 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 sufficient for the transport of the pollen, and, though I have 

 not purposely taken some of the canal water to see if it contained 



