PHAOPHYCEA 61 
Stechospermum, and Spatoglosswm is erect, flat and 
frondose, dichotomously branched, and attached at 
the base to the substratum by root-hairs. In several 
species of Zonaria the frond is procumbent and on 
its lower surface attached at many points by root- 
hairs to the surface. Padina has a procumbent 
thallus, but in its ultimate parts assumes a tendency 
to the upright habit. Dictyopteris alone has a mid- 
rib. The dichotomy of Dictyota follows the longi- 
tudinal division of the apical cell, while in the other 
genera the meristematic group divides into two at 
the point of divergence. The external layers, by re- 
peated transverse and longitudinal divisions, develop 
an epidermis of numerous small cells, rich in chroma- 
tophores, while the internal cells remain large and 
almost colourless and undergo rare and irregular 
division. The paraphyses have a basal growth, and 
occur in tufts or in rows in symmetrical fashion. 
The Reproductive Organs occur always on peculiar 
individual plants. In Dictyota and Taonia the 
plants are unisexual; in Padina both oogonia and 
antheridia occur on the same plant; while in all 
cases the non-sexual spores occur on plants which 
do not bear other reproductive organs. All three 
kinds of reproductive bodies are of similar origin. 
An epidermal cell becomes enlarged and projects 
slightly, then divides transversely, the upper portion 
being the mother-cell of the reproductive body, 
while the lower remains part of the vegetative body. 
The organs designated oogonia are united in a dense 
sorus of such cells as have been described, the con- 
tents of the reproductive cells remaining undivided 
