424 Osterhout . — On the Life- Hi story of 
of the lateral branches of the cortex. The terminal cell of 
the branch produces an abruptly recurved trichogyne, which 
makes its way to the surface, and the antherozoid unites with 
it at the tip. The trichogyne then loses its connexion with 
the trichophore, and the latter puts out one or two con- 
jugating-tubes which make their way through the medulla 
toward the tip of the frond and unite with the auxiliary cells. 
The latter are cells in the continuity of certain specialized 
lateral branches of the cortex ; each specialized branch 
contains a single auxiliary cell ; the remaining cells of the 
branch (with the exception of the basal one) develop sterile 
filaments which surround the auxiliary cell and form the 
pericarp. The auxiliary cell, after the conjugating-tube 
reaches and conjugates with it, gives rise to a mass of 
radiating filaments which bear at the ends short branching 
filaments of cells which become the spores. The basal 
portions of the radiating filaments remain sterile and con- 
stitute the placenta. Some of the filaments grow out into 
chains of sterile cells which reach the pericarp and connect 
the placenta with it. In the meantime a carpostome has been 
formed by the disorganization of some of the filaments lying 
externally to the cystocarp. 
The occurrence of numerous short proliferations on the 
tetrasporic plant is known in several of the larger Florideae, 
and naturally excites some interest. In the case of Rhabdonia 
these proliferations are independent plants, arising from the 
germination of tetraspores in position in the parent plant on 
which they occur. A point of interest is that it is not a single 
tetraspore, but the whole contents of a tetrasporangium, which 
is required to produce one of these plants. 
The formation at the base of the young plant of rhizoids 
which make their way to the medulla of the parent plant and 
form protoplasmic connexions with its cells, suggests that the 
young plants are probably partly parasitic on the parent. 
Another point of interest is the occurrence on these young 
plants, often before they are more than a quarter of an inch in 
length, of antheridia (very commonly), and occasionally of 
