524 Piercy.—The Structure and Mode of Life of a 
Trochiscia } The formation and liberation of aplanospores in the Woodford 
form takes place as follows : The chloroplast contracts and comes to lie in 
the centre of the cell (Fig. 4, A). Then the protoplasm retreats from the cell 
wall and closely envelops the chloroplast (Fig. 4, B, C). In cells containing 
granules, a certain number may be extruded during this process. The 
resulting aplanospore is generally slightly oval in shape, its average 
dimensions being 9 \x by 8 /jl ; in short cells it is frequently more pronouncedly 
oval, as though somewhat compressed longitudinally (Fig. 4, D). It usually 
remains naked until liberated, but occasionally develops a thin wall while 
still within the mother-cell (Fig. 4, E). The chloroplast is a bright green, 
and the pyrenoid often very distinct. Refractive granules frequently occur 
in the protoplasm. Occasionally, two aplanospores arise within a single 
cell (Fig. 4, E). 
The aplanospore is liberated by the rupture of a papilla, which develops 
in the longitudinal wall (Fig. 4, F-l). The aplanospore is often seen to 
protrude in this direction before the cell opens. 
The germination of these reproductive cells has not been followed in 
detail. In the normal habitat, in summer, they have been seen to elongate 
and then divide transversely. The same observation was made more rarely 
in cultures in 5 per cent, glucose solutions (Fig. 4 , k). The width of such 
juvenile filaments is much more variable than that of adult ones, usually 
being less. 
It is probable, however, that under certain conditions the aplanospores 
subdivide in two or three directions before germinating, after the manner of 
those of forma typica , since they have often been observed in pairs when 
free. Moreover, isolated packets of green cells, similar in size though of 
obscure structure, have been found in otherwise pure material producing 
aplanospores. 
Many free aplanospores were found during the summer of 1916 in 
material growing at Woodford, and during three weeks of sunshine in the 
summer of 1915 (average daily range of temperature 53 0 F.-83 0 F.) in 
material growing in 2 per cent, to 5 per cent, glucose solutions. They 
have also appeared, though not in abundance, during damp winter weather. 
Aplanospores are not formed under conditions of drought ; nevertheless, 
they can evidently resist considerable desiccation, since they were found to 
survive a dry period lasting one month, at low temperature (average range 
3i°-5i° F.), and a short period of severe desiccation in midsummer. 
5. Cell-contents. 
Under certain conditions well-defined, white, refractive granules become 
conspicuous in the cell-contents of this Hormidium. These granules are 
1 Cf. Heering, l.c., p. 46, Fig. 49. 
