76 BOTANICAL GAZETTE [JANUARY 
The dissociated cells remained up to the end of June, and then 
apparently began to disorganize. Finally they disappeared, and 
either the entire stock has died or has sunk to the bottom and 
become buried in the soil in the resting spore or polyeder stage. 
That the plants should have broken up into solitary cells and that 
they should have reached such an enormous size might have been 
thought to be due to the change of environmental conditions, like 
change in habitat, the gradual change in the density of the water 
in the tank, or changes in temperature and food. However, another 
supply of the material, collected in October in the original locality 
by Miss STEPHENS, showed that the form behaves similarly in 
nature. This material consists of the various stages as they 
appeared in the culture, from the young nets of small cells, through 
broken chains made up of a smaller number of larger cells, to the 
gollenty coenobia. Fig. 1,/, shows the last stage, in which the 
oenobium is slightly larger than those obtained in our own cultures. 
It is now clear that the form in nature passes through the same 
course of development as in our cultures in the laboratory, that is, 
there is first a net, the cells of which break apart by their own 
peculiar turgidity and looseness of connection, until finally, the 
cells which were the sides of the meshes of the net become solitary 
and live for several months as independent forms. This habit shows 
most clearly the colonial organization of Hydrodictyon. 
The soil before starting the culture in the laboratory was not 
examined for the possible presence of Hydrodictyon, but there could 
be no reason to suspect the previous existence of the plant in the 
net form in the dried condition, and therefore it must have beet 
in the resting spore condition, characteristic of green algae, or in 
the polyeder condition, if this form follows the life cycle of H.- 
reticulatum, as described by PrincsHerm. In any event, we first 
recognized a rather irregular net coming out of the soil in the tank, 
which recalls, according to PRINGSHEIM, the product of the germina- 
tion of a polyeder, though in his description the product consisted 
of 200-300 cells, while in H. africanum there are at most less than 
7o cells. The formation of new nets inside the mother cell, which 
is familiar in H. reticulatum, was not observed in this form. The 
formation of gametes was not observed in the living condition, but 
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