160 HOFMEISTER, ON 



the fruit-rudiment, causes the calyptra to break away by a 

 circular fissure near its place of junction with the vaginula. 

 The calyptra is carried upwards by the rapid elongation of 

 the fruit-rudiment, upon whose apex it is placed. 



At this period an active cell-multiplication commences 

 (especially in the direction of the thickness) in the upper 

 part of the fruit-rudiment, a little beneath the apex. The 

 cells of the apex itself take no part in this new production 

 (PI. XXII, fig. 6). When the repeated division of the 

 cells of the outer surface of the rudimentary fruit has in- 

 creased the diameter of the part nearly under the apex by 

 a certain number of cells (in Phascum cuspidatum, for 

 instance, to sixteen, in Gymnostomum pyriforme to eighteen) 

 an air-cavity in the shape of a hollow cylinder is formed 

 nearly under the outer side of the slightly swollen upper 

 end of the rudimentary fruit. This cavity divides the 

 axile portion of the rudimentary capsule from the peri- 

 pheral part, or capsule-wall. The .latter in most species of 

 Phascum has only three layers of cells (PI. XXI, fig. 5) ; 

 in Phascum bryonies and Archidium phascoides, it has only 

 two (PI. XXIII, figs. 5, 6, 8) ; in Gymnostomum pyriforme 

 it exhibits in its lower portion five, in its upper, three 

 layers of cells (PI. XXII, fig. 7). 



The primary mother-cells of the spores originate in an 

 annular layer of cells of the axile portion of the rudimentary 

 capsule. In Phascum and Eucalypta this layer is the 

 second, in Gymnostomum and Fun aria the third, reckon- 

 ing inwards from the periphery of the central portion of the 

 young capsule, which central portion is surrounded by the 

 swollen, hollow, cylindrical air-cavity. The adjoining outer 

 cells divide at a very early period by septa parallel to the 

 axis of the fruit, and most of the inner ones of the newly- 

 formed cells divide by horizontal septa (PI. XXII, fig. 8). 

 In consequence of this Phascum and Eucalypta have two, 

 Gymnostomum and Funaria three layers of cells separating 

 the hollow, cylindrical air-cavity from the layer of primary 

 mother-cells (PI. XXI, fig. 5; PL XXII, figs. 7, 10). 



When the young capsule of Phascum cuspidatum is from 

 i" to "' in length, the primary mother-cells (in which by often 

 repeated cell-production the spores are formed) surround 



