The Morphology of Ruppia Maritima. 73 
Irmisch (4858) investigated the vegetative branching of Zannichellia 
and found it to be a pure sympodium as regards its horizontal axis. 
This develops beyond its second leaf into an upright shoot, which 
ultimately bears the flowers; at its base, however, from the axil of 
the second leaf, arises a branch which prolongs the horizontal axis. 
This again, after two leaves are given off, develops into an upright 
shoot and the horizontal axis is again repeated from a branch in 
the axil of the second leaf. This process goes on indefinitely, so 
that the horizontal axis is therefore merely a succession of generations 
of axillary branches and hence a pure sympodium. 
The branching of Naias is peculiar, according to Campbell’s (1897) 
interpretation. The leaves are developed approximately in pairs— 
one slightly below the other and larger. From the axil of this 
lower one a primordium arises which by dichotomy produces a 
flower and a lateral branch. The branch bears at its base a single 
leaf. The upper leaf of the original pair is sterile, so that the stem 
of Naias has its leaves apparently in whorls of three, with a branch 
and flower arising from each whorl. Apparently the apex of the 
main stem never terminates its growth, but goes on producing its 
pairs of leaves—one sterile and one fertile—so that the system is 
very unlike that of Ruppia. 
Cymodocea, an entirely submerged marine genus, distinguished 
by its long ribbon-like leaves, very simple flowers and filamentous 
pollen, is placed by Ascherson (1889) next in order to Ruppia. 
In Cymodocea nodosa, Bornet (1864, pp. 15 ff.) describes types of 
branching which conform to those of Ruppia. The vegetative 
branching is monopodial, and a longitudinal section of the bud 
(l. c. Pl. IV, fig. 1) resembles very closely that of Ruppia. The 
flowers are terminal and the growth in length is continued by a 
lateral bud. It appears, however, that this bud is not necessarily 
one of the two buds nearest the flower. 
In Zostera the rootstock is also monopodial, the inflorescent 
system being sympodial (Sauvageau, 1891, I). 
Phyllospadix closely resembles Zostera (Dudley, 1893). 
In Althenia (Prillieux, 1864), on the other hand, a genus resem- 
bling Zannichellia and found in Europe, Africa and Australia, the 
vegetative branching is sympodial, much as in Zannichellia. The 
growth of the rootstock is continued by successive branches from 
the horizontal axis which in each case itself becomes vertical and 
bears the flowers. The flowers are unisexual—the male terminating 
the upright axis or stem. In the axils of the two leaves subtending 
the male flower arise secondary branches, which bear male or 
