170 HOFMEISTEll, ON 



figs. 5, 6, 7). This is exactly the process which in all 

 mosses causes the separation of the outer capsule-wall 

 from the inner portion. 



One of the cells of the interior of the capsule grows to a 

 considerable extent, pressing the adjoining cells together. 

 Its walls become thickened, and its contents rich in 

 granular mucilage (PL XXIII, fig. 5) . This cell is the sole 

 primary mother-cell of the spores. Its primary position is 

 always excentrical, separated by two layers of cells from 

 the hollow cavity which adjoins the inner surface of the 

 outer capsule-wall. Its vigorous power of growth con- 

 tinues whilst the surrounding tissue becomes disintegrated 

 and dissolved. It now lies quite free in the cavity of the 

 capsule, and falls out of the opened capsule without assist- 

 ance. Four freely-floating mother-cells of the second 

 degree are produced in its interior (PI. XXIII, fig. 7), 

 each of which divides into four special mother-cells (PI. 

 XXIII, fig. 8). Each of the latter produces one spore, 

 so that the whole number of spores is sixteen. I have met 

 with no exception to this in my numerous investigations. 



The diameter of the newly-formed spore measures only 

 one-sixth that of the ripe one. A delicate exosporium 

 is distinguishable even in the earliest stages of develop- 

 ment (PI. XXIII, fig. 9). Afterwards it increases consider- 

 ably in thickness, even before the entire dissolution of the 

 mother-cells and the special mother-cells. 



The inner capsule wall, and the inner cellular layer of 

 the outer wall, are present for some time after the forma- 

 tion of the spores. These masses of cells are displaced, as 

 far as the outermost cellular layer of the (now spherical) 

 capsule, by the gradual growth of the spores. The mem- 

 brane of the primary mother-cell remains to the last, en- 

 closing all the spores. It is the membrane spoken of in 

 the ' Bryologia Europsea ' as the delicate spore-sac. 



Tew processes in the vegetable kingdom are so 

 thoroughly understood as the germination of the spores 

 of mosses, the production of leafy axes from individual cells 

 of the confervoid pro-embryo. The admirable observa- 

 tions of Schimper* have entirely solved the last remaining 



* 'Recherches surles Mousses/ Strasburg, 1848. 



