THE HIGHER CRYPTOGAMIA. 281 



terminal bud,* like the first rudiment of the vegetative 

 leaf, but more massive and much less elevated. 



Definite points in this very flat annular wall become 

 prominent, after the manner in which the leaf tips 

 project above the (originally) smooth margin of the 

 sheathing leaf. A ring of hemispherical protuberances is 

 thus produced around the stem, which, in the growing 

 fruit, is clearly perceptible in the third rudimentary 

 sporangial circle, reckoning from the terminal bud down- 

 wards (PL XXXVI, figs. 3, 6). The normal cell-multipli- 

 cation of these hemispherical cellular masses — the rudiments 

 of the stalks of the sporangia — is similar to that of the 

 fruit-rudiment of Pellia (PL XXXVI, figs. 4, 5). The 

 development of their upper part soon exceeds that of the 

 lower ; by the pressure of their apices against one another 

 they assume the form of hexagonal shields. On the under- 

 side, where they pass into the stalk, these shields soon 

 exhibit at five or six points a rapid cell-multiplication pro- 

 duced by the division of one of the cells of the under surface 

 of the shield. This division takes place by septa inclined 

 in different directions, and is repeated continually in the 

 apical ceU (PL XXXVI, fig. 7). Prom five to six blunt 

 warts of cellular tissue are thus produced on the under side 

 of the shield : these are the first rudiments of the sporangia. 

 Shortly after their first appearance the growth of one of the 

 inner cells considerably surpasses that of its neighbours. 

 The cell in question is at this time only separated from the 

 apex of the young sporangium by a simple layer consisting 

 of a few cells. It is the primary mother- cell of the spores ; 

 the cells surrounding it become the wall of the sporan- 

 gium. 



The first division of the primary mother-cell takes place 

 by a horizontal septum (PL XXXVI, fig. 8). By repeated 

 bi-partition of the primary mother-cell the number of cells 

 destined for spore-formation is increased (PL XXXVI, 

 figs. 9, 10). In the mean time the number of the cells of 

 the wall increases much more rapidly : the latter soon con- 

 sists of a double layer produced by the division of its 



* The structure and mode of cell-multiplication of the terminal bud exactly 

 correspond with that of the terminal bud of vegetative shoots. 



