The Morphology of Ruppia Maritima. 67 



opposite sides of the rhachis, the latter being homologous to a 

 spadix, but not at all fleshy. The flowers are naked and consist 

 of two practically sessile anthers, each with its two large sacs or 

 thecae separate and arranged transversely on the rhachis, making 

 a diamond-shaped arrangement, in the center of which is a group 

 of pistils, always four in number in the specimens I have examined 

 (PL IX, fig. 49).^ After the shedding of the pollen, the pistils if 

 fertilized develop a stipe or pedicel of considerable length (PI. IV, 

 fig. 13). The peduncle, or floral axis, however, elongates whether 

 fertilization is consummated or not. After fertilization the fruit is 

 drawn below the surface of the water, the elongated peduncle 

 usually coiling up to aid in this process (see p. 85). 



In company with most of the submerged plants, Ruppia is per- 

 ennial. The majority of the leaves and stems die at the approach 

 of cold weather, leaving the living rootstock buried in the mud. 

 Some green leaves, however, remain, connected with the rootstock, 

 and lie at the bottom of the ditch or pool, so that it is possible to 

 collect all of the vegetative organs all winter. 



One locality, indeed, is worthy of note, where Ruppia maritima 

 flourishes aU winter. Here, possibly on account of springs, the 

 water is tempered somewhat, and I have gathered Ruppia in a 

 green, vigorous condition, when the surface of the ditch was covered 

 with ice over an inch in thickness. Although there are doubtless 

 springs here, the water nevertheless contains a large percentage of 

 salt. It is quite possible that there are many other similar locations 

 where Ruppia grows all through the winter. 



In no case, however, have I found the bulbous winter buds, 

 which have been noted in the Potamogetons by Irmisch (1858). 



As indicated by Britton and Brown (1896 vol. I, p. 79), considerable 

 variation exists in Ruppia maritima. Thus, one form which I have 

 noticed especially, is of a more slender habit, with narrower leaves 

 and stems than those of the ordinary individual. Its branching is 

 ultimately quite irregular, although the system accords with that 

 of the normal form. This form grows in quiet pools. 



There is, moreover, still considerable uncertainty as to the number 

 of existing species of Ruppia (Ascherson, 1889; Sauvageau, 1891, II, 

 p. 209 ; Roze, 1894, p. 479). The question is such a large one that 

 it cannot be discussed here, and would require, besides, a careful 

 study of herbarium material from diff"erent parts of the world. 

 I will only state that as far as I can learn from a study of systematic 



1 But see Eoze. 1894, p. 479. 



