632 SUMMARY OF CURRENT RESEARCHES RELATINO TO 



Protopliyta: 



Cellular Envelope of the Filamentous Nostocaceae.* — M. M. 



Gomout ililTers to a certain extent from the conclusions of Borzi | with 

 regard to the nature of the envelope immediately surrounding the cell 

 in the filamentous Nostacaccao, which is stated by Borzi to be inseparable 

 from the protoplasm, and to jiass insensibly into it. According to M. 

 Gomont, writers have hitherto confounded the envelope proper of the 

 cell with the mucilaginous sheath of the trichomo. Taking as a favour- 

 able example Scytonema myochroits, he finds that the mucilaginous 

 sheath can be rapidly dissolved by chromic acid of a strength of from 

 33 to 50 per cent., with the exception of a very thin external pellicle, 

 the very thin perfectly transparent envelope proper of the cell being also 

 left behind. This appears to possess properties intermediate between 

 those of the membrane of the hyphfe of fungi and those of vegetable 

 cutin. It displays a remarkable power of resistance to acids ; it is un- 

 afl'ected by the action for twenty-four hours of chromic acid of 33 per 

 cent., or of concentrated sulphuric acid ; chromic acid of 50 per cent, 

 dissolves it in a few hours. It is insoluble in potash ; with iodine re- 

 agents it never takes a blue colour, but remains uncoloured or takes a 

 light yellow tint. It takes up anilin dyes, especially fuchsin, with 

 great avidity. 



Development of Mischococcus confervicola.J — Prof. A. Borzi has 

 followed out the life-history of this Protophyte more fully than previous 

 observers. The ordinary dendroidal form, in which each branch consists 

 of two nearly spherical cells supported on a gelatinous stalk, is com- 

 monly found attached to alga3 and other water-plants. The cells have 

 thin smooth cell-walls giving the reaction of cellulose. Each has from 

 two to four chromatophores without pyrenoids, and a nucleus. In 

 addition to the ordinary dendroidal, Mischococcus has also a palmelloid 

 form, in which it spreads itself as a thin layer over the surface of the 

 substratum, dividing in two directions only; the cells being in com- 

 parison twice as large or larger. The cells of the palmelloid form 

 finally give birth to zoospores, sometimes one, more often two or four, 

 from each cell. Each zoospore has a red pigment-spot, and a single very 

 delicate cilium. On germinating they again give birth to palmelloid 

 colonies. The dendroidal colonies are the result of a tendency of certain 

 cells in the palmelloid colonies to divide in a direction parallel to the 

 substratum ; or more often they are derived directly from the germina- 

 tion of zoospores. The cells of the dendroidal colonies also give birth 

 to zoospores, either one or two from each cell, which may be described 

 as microzoospores, in contrast to the somewhat larger macrozoospores 

 resulting from the palmelloid colonies ; otherwise they are identical 

 with them. Sig. Borzi is satisfied that, at least imder certain conditions, 

 these microzoospores are zoogametes, conjugation taking place between 

 them ; the zygospores resulting from the conjugation have at first two 

 cilia. 



Stichococcus bacillaris.§ — Herr G. Lagerheim describes a variety of 

 this organism, (3 fungicola, growing on various Polyporece, and distin- 

 guished from the normal form by its cells being oval instead of cylin- 



* Morot's Joiirn. Bot., ii. (1888) pp. 43-8. 



t See this Journal, 1887, p. 448. % Malpigliia, ii. (1888) pp. 133-47. 



j § Flora, Ixxi. (1888) pp. 61-3. 



