SIPHONACEiE. 
11 
lower half, which retains its union with the branch : and now the change is complete. 
The anther thus formed consists of an isolated, curved, cylindrical, nearly colourless but 
not empty cell, supported on a pedicle of variable length and curvature. In the anther- 
cell spermatozoids are gradually evolved out of the contained matter, and are at maturity 
emitted through an opening at the summit of the cell. So much for the structure of 
the anther. The sporangium , or female organ, is placed on the branch close to the antheri- 
dium , and like it, at first consists of a papilla, or minute ramulus rising from the branch. 
It does not, however, lengthen into a cylinder, but assumes an ovoid form ; its contents 
become dense and granular ; a diaphragm separating it from the branch is formed across 
its base, and thus it becomes a separate egg-shaped cellule, sessile on the branch from 
which it has been formed. A beak-like attenuation, directed toward the adjacent 
antheridium, is now formed, and becomes at length perforated. At the same time the 
antheridium, having curled round, directs its extremity toward the sporangium ; its 
summit opens, aud the enclosed spermatozoids are discharged into the water, close to 
the orifice of the sporangium, which they enter and effect the fertilization of the matter 
aggregated within. A cell-wall is then formed round the fertilized substance, which 
thus becomes a spore, which gradually ripens and is detached on the bursting or decay 
of the membranous cyst within which it was formed. In its process toward ripening 
it loses its green colour, and at length becomes nearly colourless, except for one or more 
brown masses which it contains. In this state it remains, often for a considerable time, 
till germination takes place, when it suddenly resumes its green, and then elongates 
into a tubular cell, which assumes the form and ramification of the parent plant. 
This Order is dispersed, under one or other of its forms, over most parts of the world, 
and its species are found either in the sea, in fresh water, or occasionally on damp soil ; 
some species of Vaucheria and the curious little Botrydium being terrestrial. The 
geographical range of several species is very extensive. Codium tomentosum and 
Bryopsis plumosa are common to the Northern and Southern Oceans and to the 
Eastern and Western Hemispheres, and are both found in the warmest parts of the 
tropical seas, as well as in high latitudes of the temperate zones. Caulerpa is specially 
characteristic of the tropical ocean, where its species are numerous, some of the more 
common kinds forming the principal algoid covering of rocks or sands in shallow water. 
Some of its species are widely scattered, and others apparently limited to a few spots. 
Several of the fossil algoid plants appear to have been Caulerpce , and the fossil figured 
by Brongniart (tab. 9, bis, Jig. 1), under the name “ Fucoides hypnoidesj bears a very 
striking resemblance to Caulerpa hypnoides of the Australian coast. 
SYNOPSIS OF THE NORTH AMERICAN GENERA. 
Sub-order I. Caulerpe^e. Frond with prostrate, rooting, primary stems (surculi), and 
erect branches, membranous, unicellular ; cell within filled with a network of 
branching fibrils. 
I. Caulerpa. 
