34 
MORPHOLOGY 
immediately upon damp earth, but if under water, they form a double 
wall and become resting spores. When the aerial portion of the plant 
is exposed to drought, the contents retreat into the protected rhizoidal 
branches and round off into a 
large number of non-motile 
spores (a pianos pores'), which rest 
until the return of favorable con- 
ditions and then initiate new 
plants (fig. 93). The develop- 
ment of aplanospores is common 
among algae, being a method 
used by the protoplast of bridg- 
ing over unfavorable conditions, 
in which connection it appears 
more as a method of self- 
preservation than of reproduc- 
tion. The aplanospores in ger- 
mination give rise to new plants 
directly or to zoospores. 
The testimony in reference to the 
sexual reproduction of Botrydium is 
conflicting. It has been stated that 
the aplanospores give rise to numer- 
ous small biciliate gametes that con- 
jugate, but it is claimed that the 
gametes observed are those of Proto- 
siphon, a form which grows with 
Botrydium and closely resembles it. 
In any event, the presence of gametes 
among these simpler Siphonales is the 
important point for our purpose, and 
FIGS. 90-93. Botrydium: go, the ordi- Jt is of interest to note that thev 
nary vegetative form, showing the aerial green either conjugate or germinate as small 
portion and the subterranean rhizoidal portion zoospores. 
ofthe coenocyticbody; 91, aerial portion of the Vaucheria _ Th j s J s the very 
body converted into a sporangium; 92, zoo- 
spores; 93, the formation of aplanospores in common green felt, which occurs 
the rhizoidal region. After ROSTAFINSKI and j n coarse feltlike masses of 
WORONIN - branching filaments on damp 
soil and in fresh or brackish water (fig. 94). As in all coenocytic 
bodies, the nuclei and chloroplasts are numerous, and in this form oil- 
globules are abundant. 
91 
