BOT— Vol. I.] CAMPBELL— NAIAS AND ZANNICHELLIA. 23 



between those like N. major, where there are only stigmatic 

 lobes found, and those like N. ancistrocarpa, where two 

 distinct envelopes, perianth (?), and carpel are developed. 



The wall of the ovary is composed for the most part of 

 but two layers of cells (fig. 47) ; but the walls of the style, 

 especially at the base, are thicker. The style in our 

 species is longer than in most others and is traversed by a 

 very evident canal (fig. 47). Schumann (1892, p. 183) 

 failed to see this, but it was accurately described by Magnus. 

 While still quite young the cells at the base of the canal, 

 lining the ovarian cavity, enlarge and soon project into the 

 cavity as conspicuous papillae (figs. 48, 49). The contents 

 of these cells are very dense, and the nuclei become very 

 large and conspicuous. It is evident that they are secretory 

 cells, and the presence of a structureless substance, often 

 quite filling the cavity and staining strongly with Bismarck 

 brown, suggests that the secretion is of a mucilaginous 

 nature and is in all probability concerned with the direction 

 of the growth of the pollen-tube. The bunch of similar 

 papillae at the base of the funiculus has already been referred 

 to. The cells of the style next the canal are very narrow, 

 but the outer ones are much broader, and those at the base 

 of the style elongated radially, ,so that there is a distinct 

 enlargement of the pistil just above the ovary. In the cells 

 of the style were noticed numbers of crystals of calcium 

 oxalate, mostly octahedral in form. 



V. Pollination. 



The pollen-grains probably are carried to the stigma by 

 the movements of the water, although in the form of IVaias 

 jlexilis studied by the writer, the position of the open anther 

 would allow of their falling spontaneously upon any female 

 flowers that might be situated below them. Jonsson (Mag- 

 nus, 1889, p. 216) concludes that this is regularly the case, 

 the pollen being heavier than the water and striking upon 

 the female flowers which are placed lower down. Magnus' 

 objection, that the male flowers stand upright and so pre- 



( 3 ) June 2, 1897. 



