1877.] Reproduction in Fresh- Water Alge. 519 
will reach the opening at the same time when there is room for 
the passage of only one at a time, and even here among these 
protoplasmic forms there seems to be an exhibition of selfishness 
often bordering on wrath. 
(Fie. 90.) PEDIASTRUM. 
The family to which the Pediastrum belongs is distinguished 
by each cell forming a large number of motile spores, which re- — 
main together as they paa 
escape, and grow into 
a new disk-shaped clus- 
ter. In Figure 90 
(which is a copy from 
A. Braun) is shown 
ner seen at a. Soon 
after the escape of a 
cell’s contents a form ; 
as shown at b is as- (Fra. 91.) VAUCHERIA. 
sumed, the cluster being surmounted by a mass of jelly. A more 
advanced state of development is given at c, where the form of 
the mature community is discerned. 
The genus Vaucheria is a large one, and is made up of species. 
of green, single-celled, often branching alge, which grow most 
frequently on the moist borders of fresh-water streams. These 
Plants are pleasant ones to study, and exhibit very well both 
_ Sexual and asexual methods of reproduction. At a in Figure 91 is 
àn enlarged portion of a filament, from the tip of one branch of 
