OOSPORES. 
279 
so that these pieces, forming small projections, give to the upper end of the cell the 
appearance of consisting of caps placed one over another, while the lower end of the 
cells appears to be enclosed in a long sheath (the lower old piece of cell-wall). This 
lower part of an elongated cell is always separated by a septum from the upper cap- 
bearing piece (see Fig. 17, p. 22). In Bulhochxte the growth of all the shoots, even of 
the first which proceed from the spores, as far as it depends on cell-multiplication, 
is limited to the division of their basal cell ; it follows therefore that the cells of each 
shoot must be considered to be the basal ceils of the lateral branches which stand upon 
FIG. 182. — Development of 'the zoogonidia of 
(Edogonnnn (after Pringshehn). A, B their origin 
from an older filament ; C free zoogonidium in 
motion ; D commencement of its germination ; 
E a zoogonidium formed out of the entire contents 
of a germinating plant ( X 350) . 
Fig. 183. — A Qidogonittm ciliatiim (X 250) middle part of a sexual filament 
with an antheridium (m) at the upper end, and two fertilised oogonia (og) and 
a dwarf male plant in; B oogonium at the moment of fertilisation; o the 
oosphere, z the antherozoid in the act of forcing its way in, ni dwarf male 
plant; C ripe oospore; D piece of the male filament of O. gejnelliparitni, 
z antherozoids. E branch of a hybernated plant of BiUbochate intermedia, 
with one oogonium still containing a spore, another in the act of allowing it to 
escape ; in the lower part an empty oogonium. F the four zoospores result- 
ing from an oospore ; G zoospores from an oospore come to rest (after 
Pringsheim). 
them. The cells contain chlorophyll-grains and a nucleus in a parietal layer of proto- 
plasm. The zoogonidia, as well as the oogonia and antheridia, are formed from cells of the 
filaments, which only become enlarged and assume a more or less spherical form when 
they give rise to oogonia. From the oospores which have remained at rest for a con- 
siderable period several (usually four) zoospores are immediately formed, which produce 
asexual, i.e. zoogonidia-forming plants, from which again similar ones proceed, until the 
series of them is closed by a sexual generation (with formation of oospores) ; but the 
sexual plants produce zoogonidia as well. The sexual plants are either monoecious or 
dioecious ; in many species the female plant produces peculiar zoogonidia (Androgonidia), 
