Pees VP Are oe -- 345 
walls. Some of these filaments enter the animal on which the 
plant is growing and absorb nutriment, while others radiate out 
in the water and produce reproductive 
structures. 
Reproduction. Saprolegnia reproduces 
asexually by the formation of zodspores 
with two cilia. These are produced in 
zodsporangia which are formed from the 
ends of club-shaped filaments (Fig. 357). 
The terminal portion of the filament is cut 
off by a cell wall, thus forming a zoésporan- 
gium, and the contents divide and round up 
to form zoospores. These escape through 
an opening at the tip of the sporangium. 
Under favorable circumstances they finally 
grow into new plants. 
Sexual reproduction is by means of 
oogonia and antheridia (Fig. 358). The 
odgonia are rounded structures which con- 
tain eggs and are cut off from the vege-' 
tative filaments by cross walls. The 
antheridium is a tubular branch which is 
cut off from the end of a hypha. It grows 
around an oogonium and produces branches 
which enter the odgonium and reach the 
eggs. In some cases a nucleus from an 
antheridium enters an egg and fertilizes it. 
Saprolegnia shows various degrees of 
loss of sexuality. In some cases, as Just 
described, the eggs are fertilized by the 
antheridia. In other cases there are both eggs and antheridia, 
but the antheridia do not fertilize the eggs, the latter develop- 
ing without fertilization. In still other cases no antheridia are 
formed. Some of the Odmycetes, with a method of sexual repro- 
duction similar to that of Saprolegnia, live as parasites in the 
leaves and stems of flowering plants. 



as 
i 
Des 
eo 
: 
ce 







ame 


a x 
eece 

alae 




. 
ne 
ot 
euGse, 
Oo ates 



Sve 

Fia.357. Immature and 
mature zodsporangia of 
Saprolegnia. (x 230) 
