412 
Osterhout. — On the Life-History of 
arise as follows : one of the lateral branches composing the 
cortex cuts off, usually midway between the medulla and 
the surface, a single cell which is situated on the upper 
side of the branch. This cell divides in a plane parallel 
to the long axis of the branch which bears it, and the upper- 
most cell divides in its turn, so that a three-celled branch 
is formed, which is directed obliquely upward and inward 
(Fig. to). Occasionally four- and five-celled procarpic branches 
are found. The development of the trichogyne begins with 
the formation of a small papilla filled with protoplasm, which 
is clear and free from granules (Fig. 15). It elongates 
slightly, and then recurves abruptly on the cell which bears 
it, the trichophore, so that the tip is directed towards the 
surface of the frond (Fig. 10). It grows directly outward 
towards this, occasionally making a more or less complete 
spiral turn, and finally reaches the surface and protrudes 
through the gelatinous covering of the frond (Fig. 11). In 
the meantime it has elongated considerably at the base, so 
that the point at which it recurves is further from the 
trichophore than it was originally (Figs. .10 and 11). The 
whole trichogyne is at this time filled with clear protoplasm 
nearly free from granules, and with few, if any, vacuoles. 
The wall is very delicate, and is surrounded by a gelatinous 
layer, often as thick as the trichogyne (Fig. 11). During its 
growth the trichogyne has a more or less swollen tip, but 
when it reaches the surface the tip appears no longer swollen 
but of about the same diameter as the rest of the trichogyne 
and slightly tapering. 
The protoplasm of the trichophore, which is at first free 
from granules and vacuoles, acquires vacuoles as the tricho- 
gyne develops, and becomes more or less granular. The 
cells of the procarpic branch below the trichophore contain 
reduced chromatophores with sometimes a mere trace of 
colour, but are usually without any colour whatever. Their 
protoplasm very early becomes vacuolate and granular. 
Occasionally one of them (in the majority of cases the one 
next the trichophore) bears a lateral cell. 
