THE HIGHER CETPTOGAMIA. 427 



the same, even in species which differ widely as to the 

 period of development. 



In the Abietinese both the cells — -whose form is that of 

 the longitudinal moieties of a blunt cone, with a convex 



"... 



basal surface — either divide again immediately by longi- 

 tudinal septa at right-angles to the one last formed (PI. LX, 

 figs. 11, 1.2 ; PL LXI, fig. 3), or else a division first occurs 

 in each of them by transverse septa perpendicular to the 

 longitudinal axis of the corpusculum, by which the cells are 

 divided into two very unequal portions, the upper one being 

 much the largest. In the lower, smaller ones of the newly- 

 formed cells, which contain much more concentrated mu- 

 cilage than the upper ones, the division by longitudinal septa 

 then ensues, which latter septa are perpendicular to the 

 septum dividing the two cells (PI. LXI, fig. 6). The latter 

 phenomenon is the most common. 



The pro-embryo now consists of two pairs of two-celled, 

 parallel rows of cells, having their edges of contact rect- 

 angular. The number of its cells is increased by repeated 

 division of each of the (lower) terminal cells by means of 

 septa at right-angles* to the longitudinal axis of the organ. 

 It is a rule without exception that the lower of the newly- 

 formed cells are the smallest, but the richest in formative 

 matter. The pro-ernbryo up to this time occupies only a 

 proportionably small space, rilling the lower part (a tenth 

 to a fifth part) of the corpusculum. As the development 

 of the pro-embryo has stretched the lower part of the cor- 

 pusculum downwards whilst its upper part remained sta- 

 tionary, the portion of the corpusculum which is filled by 

 the pro-embryo bears a much larger proportion to the 

 upper part, than the portion occupied by the germinal 

 vesicle w T hen first impregnated. The pro-embryo exhibits 

 no upward growth. The lateral walls of its uppermost 

 oldest cells are as intimately amalgamated with the inner 

 wall of the corpusculum as the thickening layers of the 

 same wall are with one another. 



* Speaking more accurately we might say, transverse septa radial to the inner 

 wall of the corpusculum. They are often strongly inclined downwards from the 

 longitudinal axis of the pro-embryo, and are thus convex upwards (pi. lx, fig. 13 ; 

 pi. lxi, fig. 16) ; the position at right angles to the axis of the organ is first 

 assumed by them after the subsequent longitudinal and transverse expansion of 

 the latter. 



