1 1 8 Chodat . — On the Polymorphism of the Green 
The appearance of the chromatophore when the Cysto- 
coccus form is developed, or in a free condition, is, as usually- 
described, somewhat stellate and always with an incision 
on one side. By division this appearance often changes into 
that of a flat cup, the upturned edges of which cause the cells 
to look as if there were parietal chromatophores. 
I cannot sufficiently insist upon the fact that all these 
various formations are not only found separate and combined 
on the same spot of bark, but even on the same thallus. 
Besides the formations here mentioned, the student can 
follow step by step in older and more concentrated cultures 
the development of very curious gelatinous conditions which 
are very similar to the genus Hormotila described by Borzi. 
To sum up: Pleurococcus,vc\ the various conditions of its 
evolution, may develop branched filaments, sporangia with 
zoospores, gametes, and spores. This is sufficient ground for 
removing this plant from the order Protococcoideae, and con- 
sidering it as a type of the Chaetophoraceae, reduced owing 
to its existence as a lichen-gonidium. 
In this order isogamy only has been described. In a recent 
paper one of my assistants, Dr, J. Huber 1 , has carefully 
studied the curious heterogamy of Aphanochaete , of which 
I had at the critical moment collected specimens growing on 
Oedogoninm. In this epiphyte the central cells of the bilateral 
thallus become greatly developed and produce oogonia. At 
this time the latter, like the other cells, are provided with 
a typical hair. The cells of the periphery contain the 
antheridia, which are much smaller and paler, sometimes 
colourless, and grouped in a very similar manner to the 
antheridia of Coleochaete. The oosphere, which is five to six 
times larger, is set free by the swelling of the inner side of 
the cell-wall and the rupture of the upper part of the 
oogonium. The expulsion takes place suddenly, and the large 
quadriciliate gametes remain enclosed in the mucilaginous 
hyaline vesicle, as is the case with the zoospores of the same 
1 Huber, Sur 1 ’ Aphanochaete repens , Soc. Bot. de France, Sess. extraordinaire en 
Suisse, 1894. 
