82 HOFMEISTER, ON 



ridges, which by their ultimate confluence become the 

 septa of the special mother-cells, are clearly perceptible 

 (PL XII, fig. 10). These special-mother-cells in Frullania 

 dilatata exhibit delicate pits (Tiipfel) similar to those of 

 Anthoceros jmnctatus. 



The wall of the half-ripe capsule of most Jungermanniae 

 consists of a double layer of cells {J. bicuspidata, triclio- 

 <phylla i Frullania dilatata, Radula complanatd). As the fruit 

 approaches maturity the inner of these cellular layers is 

 usually dissolved, and displaced by the growing spores. 



The individualization of the cells of the interior of the cap- 

 sule depends, as in all similar cases, upon a highly advanced 

 state of this change in the properties of the substance of the 

 wall of the outer layer of the affected cell-membrane. There 

 exists, however, a striking difference between what occurs in 

 Jungermanniae, and the analogous processes in the develop- 

 ment of the spores of other mosses and vascular crypto- 

 gams, and of the pollen-cells of Phanerogamia. In 

 Jungermanniae a thick layer, constituting almost the 

 entire mass of the cell - membrane, undergoes trans- 

 formation into a substance which becomes distended 

 in water into a gelatinous mass, and disperses itself 

 through the fluid; -whilst in other cases this modifica- 

 tion of the cell-membrane is limited to an immeasurably 

 thin external layer. In many cases, even in Jungermanniae, 

 the condition of the different layers of the mother-cell- 

 membrane during the distension varies. In Fossombronia 

 pusilla the inner layer of the wall of those cells which are 

 exclusively developed into elaters is so vastly distended by 

 water w T hen in a young state, that it bursts the outer layer 

 of the cell-membrane (PL VI, fig. 36). The same state of 

 circumstances, somewhat modified, occurs in the mother- 

 cells of the same plant, where, however, the less-distendible 

 outer layer is so thick that it does not burst ; the expansion 

 of the inner layer takes place at the expense of the volume 

 of the cell- contents, which are compressed into a smaller 

 space (PL VI, fig. 35). In Blasia pusilla also the mem- 

 brane of the cell, from the division of which two spore- 

 mother-cells have arisen, and which is very often present 

 after the formation of the tertiary nucleus, resists the action 



