CHLOROPHYCEAi 169 
motionless spores within large sporangia. These spores, 
which are round and provided with a membrane, do 
not germinate in the ordinary way but become them- 
selves small plantlets with a rhizoid attachment. 
These either soon give rise to a filamentous thallus, 
or, becoming enlarged, are transformed into new 
sporangia, the actual outcome of which has not yet 
been observed. 
In Urospora and Rhizoclonium there is a method of 
vegetative propagation by the separation of vegetative 
cells densely packed with con- 
tents. In Urospora the filament 
breaks up first into multicellular 
parts and eventually into single 
cells. These either germinate 
directly or, after surrounding 
themselves with thick walls and 
resting, produce zoospores. In 
Rhizoclontwm the process 1s sim- 
ply that of the cells becoming 
rounded and dropping off; they 
germinate by the production of a 
filament in all cases. 
The Geographical Distribution. 
—Cladophora has a world-wide 
distribution in both salt and 
fresh water. Chetomorpha 1s 
also extensively distributed, but 
mostly in the sea. Rhizoclonium 
has a similar distribution to 
Cladophora. All three genera 
Fic, 52. — Cheetomorpha 
Darwini (reduced). 
are represented by numerous species, many of them 
