164 HOEMKISTER, ON 



water powerfully. If a thin section of these cells is placed 

 in water, very active currents may be observed over these 

 cells, and in their interior. 



In Gymnostomum ovatum the affinity of the substance of 

 the walls of the tertiary spore-mother-cells for water is 

 even stronger than in Phascum cuspidatum. If these 

 cells are placed in water, the substance of the cell-mem- 

 brane is almost immediately distributed through the fluid, 

 so that the cell-contents remain behind, a shapeless, dis- 

 solving, round mass. In order to get a sight of these 

 thick cell-membranes, it is necessary to observe the cells 

 with the greatest promptitude immediately after they have 

 been prepared for the microscope. On rare occasions the 

 outermost lamella of these membranes holds together for a 

 somewhat longer period in the form of a sac open at one 

 end, after the rupture, by pressure, of the more highly 

 swollen inner layers. 



The contents of the mother-cell of the spores of Phascum 

 divide into four portions, which after some time become 

 clothed with a stiff membrane, and shrivel up under the 

 action of alcohol. The first indication of this division 

 is the appearance of a transparent line in the turbid cell- 

 contents, passing transversely through the cell (PI. XXII, 

 fig. 2), or of two such lines cutting one another at right 

 angles (PI. XXII, fig. 3). The contraction of the contents 

 manifestly occurs for the first time after their division into 

 halves. The opacity of the cell-contents entirely prevents 

 the observation of the behaviour of the nucleus of the spore- 

 mother-cell during the formation of the spores. 



The young spores lie in fours quite free in the mother- 

 cell (PI. XXII, fig. 4). Each spore exhibits a central 

 nucleus, with a manifest nucleolus (PI. XXII, fig. 5). The 

 cell-contents consist of proteine combinations, dextrine, and 

 starch- granules. Afterwards, when the formation of the 

 exosporium commences, (at which period the absorption of 

 the spore-mother-cells begins), oil- drops are visible in the 

 interior of the spore, which, as the spore becomes mature, 

 increase in number and size. During the time that the 

 spores lie free between the inner wall and the columella, 

 the cells of the innermost cellular layer of the former, and 



