BoT.— Vol. I.] CAMPBELL— NAIAS AND ZANNICHELLIA. 17 



and several other species have normally four loculi. On 

 page 24 of his memoir, Magnus states that he had earlier 

 supposed that N. tenuifolia had two loculi, and that the same 

 might possibly be the case in N. indica Willd. and N. 

 graminea Del. He concluded, however, on the basis of 

 later investigations, that he had been mistaken, and that 

 there were really four loculi in these species. In one or 

 two instances the writer found specimens of N. jlexUls where 

 the cavity of the anther was completely divided by a longi- 

 tudinal partition (fig. 29), and several interesting interme- 

 diate conditions were met with, one of which is shown in 

 fig. 16. This indicates that the uni-locular condition is the 

 original one, and that the pluri-locular condition has arisen 

 secondarily by the conversion of some of the originally 

 sporogenous tissue into a septum, as Bower (1894) ^^^ 

 pointed out in some other cases. 



(/5) The Gei'mination of the Pollen. — The ripe pollen- 

 spores are elongated and contain much starch in large gran- 

 ules, more or less obscuring the other contents. The pollen- 

 tube is formed either at one end or laterally (figs. 30, 31) ; 

 into it pass most of the granular contents and the two gen- 

 erative nuclei. The history of the vegetative nucleus was 

 doubtful, but it probably may either pass into the tube or 

 remain in the spore. In either case it appears to be finally 

 disorganized. As the pollen-tube grows, the starch is grad- 

 ually used up, the growth being apparently entirely at the 

 expense of the reserve starch, and not at all from the cells 

 of the pistil until the cavity of the ovary is reached. The 

 plugs of cellulose so common in pollen-tubes are also found 

 here. The growth of the pollen-tubes was quite as often 

 upon the outside of the style as through its canal and seemed 

 quite independent of any nutriment which the tube derived 

 from the cells of the style. 



2. The Female Flower. — The fully developed female 

 flower in Naias jlexilis consists of a single carpel, enclosing 

 a solitary anatropous ovule (fig. 44). The ovary is but 

 slightly enlarged and is prolonged above into a somewhat 

 tapering style. At the apex are four lobes, two of which 



