THE HIGHER CRYPTOGAMIA. 385 



of it (PI. LIV, fig. 3). The mode of cell-multiplication in 

 the growing end of the fruit-branch resembles that of the 

 terminal bud of vegetative shoots (PL LV, fig. 29), with 

 this difference only, that the growth in thickness is uniform 

 on all sides. The transverse section of the fruit-branch is 

 circular not elliptical. 



A sporangium is produced in the axil of each of the 

 equal-sized leaves of the fruit-branch — which leaves have 

 the 2^ arrangement — with the exception of the two or three 

 first, lowest leaves. The first rudiment of the sporangium 

 is produced by the division, by means of a septum almost 

 perpendicular to the outer surface of the terminal bud, of one 

 of the cells of the circumference of the stem close above the 

 middle point of the place of attachment of the youngest 

 leaf. This is followed by the production of septa at right 

 angles to that surface in the sporangial cells of the second 

 degree, and of septa parallel to it in the sporangial cells of 

 the third degree (PL LV, figs. 1, 2). As soon as 

 the organ has the appearance of a hemispherical lateral 

 outgrowth of the end of the stem, a central cell may 

 be seen, surrounded by a simple layer of cells, and borne 

 upon a short stalk consisting of a few cells. In Belaginella 

 helvetica this central cell is much larger than its neighbours 

 (PL LIV, fig. 2). In S. hortensis the cells which bear it 

 divide for the first time at a late period by septa paraUel to 

 the longitudinal axis of the sporangium. In this species 

 the cell in question appears as the uppermost of a string 

 of cells traversing the axis of the rudimentary sporangium 

 (PL LV, fig. 3). 



The enveloping cells divide repeatedly by septa perpen- 

 dicular to the outer surface of the young fruit, alternating 

 twice with septa parallel to that surface. The wall of the 

 sporangium soon becomes a double cellular layer and ulti- 

 mately a triple one (PL LV, figs. 4 — 6). The cells of the 

 stalk also divide repeatedly by septa parallel to the longitu- 

 dinal axis and perpendicular to it ; the stalk of the sporan- 

 gium rapidly becomes both longer and thicker. In the 

 mean time the central cell also multiplies, although more 

 slowly, by repeated bipartitions in all three directions 

 (PL LX, figs. 4, 5). In a mass of fruit of Selaginella 



25 



