THE HIGHER CRYPTOGAMIA. 27 



The multiplication of the cells of each shoot in the 

 direction of its longitudinal axis takes place exclusively in 

 the cells of the fore edge. In the young germ-plant they 

 divide, as has been shown above, by septa inclined to the 

 horizon alternately in different directions. The form of 

 the cell-multiplication in the fore edge of the growing- 

 shoots of older plants is essentially different. Here the 

 marginal cells divide by septa which are parallel to one 

 another, slightly convex on the inner side, and perpendi- 

 cular to the surfaces of the plant. This form of division 

 often occurs in young germ-plants of two months old 

 (PI. IV, fig. 24). The phenomenon which occurs so fre- 

 quently, viz., the fact that in the earliest stages of develop- 

 ment the division by horizontal septa parallel to one an- 

 other* precedes that which in all subsequent stages is the 

 normal mode of cell-multiplication, viz., division of the 

 terminal cell by septa alternately inclined in different direc- 

 tions, makes it probable that the latter form of cell divi- 

 sion is to be looked upon as a more perfect, higher form of 

 growth than the former. Still more remarkable is the 

 fact (which as yet stands alone), that in Pellia the simple, 

 apparently lower form of cell-multiplication follows, in 

 point of time, the more complex form which occurs in the 

 later periods of the life of the plant. 



This phenomenon appears most distinctly in the first 

 spring-shoots of fruiting specimens. Here the cells of the 

 fore edge of the first, second, and third order exhibit, 

 during the growth of the shoot, large and manifest nuclei, 

 from which mucilaginous threads often pass to the walls of 

 the cells; they contain, besides, a slightly granular, yellowish 

 slime. In the older cells lying- behind the fore edge, 

 numerous small chlocophyll-granules make their appear- 

 ance ; the nuclei of these cells are less easily seen (PI. IV, 

 fig. 25). The cell of the first order the terminal cell- has 

 the form of a slice taken from the middle of a double convex 

 lens by two sections parallel to the small axis ; the cell of 

 the second order, at its first appearance, is shaped like a 



* This occurs in the prothalHuin of mosses, in the suspensor of Selaginella, 

 in the greater number of phsenogans, and in the rudiments of the fruit of 

 many mosses. 



