THE HIGHER CRYPTOGAMIA. 39 



ened than in its other parts. Six bands are formed, 

 which are attached to the inner wall, and protrude inwards. 

 At their first appearance, in the middle of September, they 

 are tolerably flat, but increase slowly in height until the 

 beginning of December (PL V, fig. 17). The median space 

 by which the four protuberances of the mother-cell are in 

 continuous communication * is thereby narrowed ; rather 

 narrow circular cavities lead from it to the four protuber- 

 ances. It is now filled exclusively with transparent fluid 

 matter as clear as water ; chlorophyll-granules and granules 

 of mucilage are as yet found only in the protuberances. 

 Suddenly each of the latter appears separated from the 

 quadrangular median space of the mother-cell, by a wall 

 convex towards the interior (PI. V, fig. 17). This delicate 

 membrane is probably not mounted upon the edge of the 

 broad ledge which protrudes into the median space, but 

 clings to its surface, and encloses the entire contents of 

 the protuberance, which, consequently, now represents a 

 very delicate- walled oval cell, i. e. the young spore. By 

 the dissolution of that portion of the wall of the latter 

 cell which belongs to the protuberance of the mother-eell, 

 the space very soon becomes free ; I have reason to sup- 

 pose that this occurs within forty-eight hours after the 

 spore has become individualised. The six thickened bands, 

 on the other hand, which consist of glass-like cellulose, 

 and which unite to form the skeleton of an uneven-sur- 

 faced quadrangular figure, last for several days ; they are 

 to be found in large numbers amongst the escaped spores, 

 and are most elegant microscopical objects (PI. V, fig. 20). 

 The spores of Pellia exhibit in the course of their develop- 

 ment several peculiarities, which are of importance in the 

 study of cell-formation. That the walls of the special 

 mother-cells grow gradually inwards from the inner wall of 

 the mother-cell is placed beyond a doubt, as well by the 

 slow growth of the bands above mentioned, as also by the 

 fact that, in Pellia, the walls in question are normally only 



* This appears perfectly clearly when one of the protuberances of a mother- 

 cell which lias been lying in water bursts, and a portion of the contents escapes 

 through the fissure (a very frequent occurrence). The fluid contents of the 

 uninjured protuberances of the mother-cell then flow slowly, mixed with chloro- 

 phyll-granules, into the one which has been ruptured. 



