130 A. H. Graves, 
horizontal direction, around the rhachis, closely following its sur- 
face, until finally they nearly meet, as in Pl. IX, fig. 49. 
The pistils, occurring between the thecae in a group of four, form 
a diamond-shaped pattern arranged in a transverse position on the 
rhachis. Each pistil develops, in the mature flower, into a cyl- 
indrical structure tipped with a sessile peltate stigma and con- 
taining a single ovule. 
As regards the number of the pistils, I have never found it to 
vary; but Ascherson (1889), who divides Ruppia maritima, his only 
species of the genus, into three subspecies, says in his generic 
characterization, “4 (selten bis 10)”. Roze (1894, p. 479), indeed, 
makes the number of pistils the main specific difference between 
R. maritima and Rk. rostellata, allegmg that the former has eight 
pistils and the latter four. In this vicinity, however, Ruppia maritima 
seems to have always four. 
Eichler (1875, p. 89), Irmisch (1851), and other older authorities 
do not hesitate to allude to the subfloral leaves of Ruppia (the pair 
at the base of the inflorescence) as the spathe leaves. This homol- 
ogy is not used, however, by more recent authorities. For reasons 
already adduced, I have applied to them the name of subfloral 
leaves. As to the spathe, however, it seems quite probable that 
a rudiment of it is represented in the floral scale leaf. As has been 
shown (pp. 99-102), its manner of origin, development orientation, 
etc. all connect it ultimately with the flower, and although its mor- 
phological origin is clearly identical with that of a vegetative scale 
leaf, its relations to the spadix indicate a spathe-like nature. Since 
the flower of Ruppia represents a much reduced type, we should 
expect to find such reduced structures here.! 
FroraL DEVELOPMENT 
With these remarks on the general morphology of the mature 
flowers, I shall describe briefly the developmental stages of the 
young flower, from the time when it is first recognizable until about 
the period when the archesporial cells first appear. From that 

+ | have already indicated (p. 101) that Irmisch overlooked this spathe- 
like floral scale leaf, and I had been unable to find any reference to it 
in the literature. At the last moment, however, I find that Griffith (1851 
I, pls. 257, 258 and 259; II, pp. 196 and 198) figured and described this 
structure, considering it a true spathe, and explaining its origin and 
development essentially as I have done. 
