LIFE HISTORY OF A FILIFORM ALGA. 
89 
LIFE HISTORY OF A FILIFORM ALGA 
(CVDOGONIUM). 
BY M. C. COOKE, M.A., A.L.S. 
(Continued from page 76.) 
Having for the time disposed of the ordinary cells 
such as are observed in both the sterile and fertile condition 
of the plant, we now return to the microscope and look along 
the threads in search of any divergence from this ordinary 
condition of vegetative cells. And, supposing the threads to 
be in the fertile state in which we found them, we soon 
become conscious of the presence of certain special cells 
interspersed amongst the rest, which are broader, more oval, 
and contain within them not the granular cell contents, but 
a large, opaque, definite, somewhat globose body, of a dark 
colour, which we will call a spore. Its proper designation is 
oospore, or a spore produced in an ovarian sac, or cell, which 
sac, or cell, is termed the oogonium. The oogonium is a little 
larger than the oospore but of the same form, and the oospore 
lies free within it, being at first greenish and granular but at 
length invested with a brown coat, which again has an outer 
transparent layer more or less thick, according to the species. 
Concerning ourselves only with this one species of (Edoyonium , 
we find it producing nearly elliptical brown oospores, with a 
very thick hyaline outer coat, hence called crassiuscidum. One 
PLATE III. 
Description of the Figures. 
Fig. 1.—Illustrations of the growth of new cells. At a it has just 
commenced 1 , leaving a ring at the apex of the daughter cell ; 
b, the daughter cell has attained an equal size to the mother 
cell; at c a second new cell has commenced, bearing the first 
and second ring at its apex, x 200. 
Fig. 2.—Asexual reproduction; a, zoospore being formed in mother 
cell; b, zoospore escaping by rupture of the mother cell; 
c, germinating asexual zoospore, x 200. 
Fig. 3.— a, androsporangia of ffi. crassiuscidum ; b, androspore; c, the 
same, with the cilia absorbed ; d, <?,/, g, successive stages in 
the development of dwarf males from the androspore; 
h, spermatia. x 200. 
Fig. 4.— a, portion of filament of the CEdogonium, with oospore in the 
oogonium, and four dwarf males attached to the supporting 
cell; b, c , d, formation of four sexually produced zoospores 
from the fertilised oospore ; e, zoospore at rest, and attached 
at its base ; /, commencement of growth of the first cell of 
the young (Edogonium . x 200. 
