16 



ON NAIAS GRAMINEA DEL., VAE. DELILEI MAGNUS. 



FlS. 70. 



In its early stage the lower, or flask-shaped, 

 portion consists of a globose or ovate body, 

 surmounted by a flat parallel-sided band, of 

 nearly the same breadth as the lower portion 

 (fig. 67). The upper portion or neck of the flask 

 divides about half-way up into two divisions, like 

 the stigma of an ordinary flowering plant (see 

 fig. 71). This stigmatoid portion attains its 

 maximum length very early. The basal portion 

 contains a single anatropous ovule, and it en- 

 larges both outwards and upwards until it is twice 

 the length of the style-like portion (see fig. 70). 



The investing membrane (fig. 88) — which can 

 be removed like the calyptra of a Polytrichum — is 

 made up of one or two layers of cells, which vary 

 in shape according to their position. The portion 

 which covers the ovule consists of elongate cells 

 with truncate ends, and these cells are densely 

 packed with rounded grains of starch very uniform 

 in size. The starch makes its appearance in the 

 later stages of the growth of the membrane. The 

 portion which covers the long neck of the flask- 

 shaped body is also mostly composed of long 

 cells ; but the cells which occur on the margins of the stigmatoid 

 divisions of the free ends are only one-third the length of the 

 central cells, and their outer ends are somewhat enlarged so as to 

 make the edge of the stigmatoid divisions minutely papillate, as if 



to afford better attachment for the 

 grains of pollen (fig. 72). The cells 

 of the base of the neck are much 

 broader than any of those in other 

 parts of the investing membrane, and 

 they are also more loosely aggregated 

 at that point. 



A central canal runs throughout 

 the narrow" portion which simulates 

 the style, and at the point where it 

 reaches the chamber which contains 

 the ovule it becomes slightly con- 

 stricted (fig. 71); but immediately 

 below the constriction it widens out 

 into a cupola-shaped cavity, whose 

 upper portion or roof is lined with a few unicellular hairs (figs. 

 72 and 73). Below this cavity is the ovule. The accompanying 

 drawings (figs. 67 to 73) illustrate the female flower in some of its 

 stages of development. 



No portion of the pistilliferous flower bears any spines similar 

 to those which oocur on the bracts and leaves ; such spines are 

 present in some of the species of Naias. 



Pm.71. Fie. 72. Fig. 73. 



