312 THALLOPHYTES 
duce a new plant directly but, as in Hydrodictyon, produces 
a number of zodspores each of which produces a new plant. 
Thus, instead of one, a number of new plants arise from the 
zygospore, a feature of advantage in the multiplication of new 
plants. 
Another form, similar in a number of ways to Ulothrix, is 
Cladophora which has long 
branched filaments that 
form long, green, hair-like 
tufts, which, with one end 
anchored to a stone or some 
other object, wave back and 
forth in moving streams. 
The cells are multinucleate 
and contain many chloro- 
plasts. Reproduction is by 
zoospores and isogametes, 
but the zygospore develops 
a new plant directly. 
Oedogonium.— This form 
(Fig. 268), common in lakes 
and ponds, is similar to Ulo- 
thrix in the character of the 
filament, but shows marked 
advancement in methods of 
Fic. 268.— Oedogonium. A,a portion reproduction. The zo- 
of a filament of Ocdogoniwm echinosper- ospores, formed only one in 
mum, showing some vegetative cells and g cel] and consequently very 
odgonium above and some antheridia be- a 
large, have numerous cilia 
low from which sperms are escaping; B, a 
portion of a female filament of OZ DOGO- forming a crown at the for- 
NIUM HUNTII, showing odgonia and wardend. Sexual reproduc- 
two dwarf male plants attached near the tion is distinctly heteroga- 
odgonia; (’, zodspores of an Oedogonium mous. Th . 
: ; e eggs, which are 
escaping from the cells of the filament. 1 a = a Eh Fao 
x about 300. Drawn from Wolle. arpe one) paces ye 200; 
are borne in much enlarged 
cells called odgonia. Each oégonium bears one egg and is simply 
a transformed vegetative cell of the filament. Other small cells 
produce the sperms which resemble the zodspores except in size. 
The sperms swim to the oégonia, enter, and fertilize the eggs and 
thick-walled resting odspores are then formed. Upon germina- 
