THE HIGHER CRYPTOGAMIA. 59 



more than simple cells, produced by the cutting off 

 of short papillae by a transverse septum. This renders 

 it in the highest degree probable that a single cell of the 

 bounding surface of the stem is the mother-cell of the leaf. 

 However at the period when the young leaf first appears 

 above the surface of the stem, it consists, when viewed from 

 above, of four cells arranged side by side, embracing more 

 than a fourth part of the stem (PI. IX, fig. 14). The two 

 middle ones are considerably larger than the side ones. 

 The foundation for the two-pointed form of the leaf is 

 laid immediately upon the division of the middle cells by 

 septa, both at right angles to the median line of the leaf, 

 and diverging from it to the right and left. Each of the 

 two middle cells of the 4 -cellular fore-edge of the leaf 

 developes a papillaeforni prolongation, directed forwards 

 and at the same time obliquely outwards • the outline of 

 each is parabolical, and each of them divides repeatedly by 

 transverse septa (PI. IX, fig. 15). The wide and low 

 interstitial cells thus produced are divided from once to 

 as many as eight times by septa parallel to the longitudinal 

 axes of the teeth of the leaves. The activity of this cell- 

 multiplication diminishes from below upwards ; the tips of 

 the teeth of full-grown leaves consist of short simple rows 

 of cells. During the formation of the teeth, the number 

 of the cells of the lower part of the leaf continues to increase 

 considerably by longitudinal and transverse divisions. The 

 septa there formed are not always at right angles, or parallel 

 to the longitudinal axis of the leaf, but are often laterally 

 inclined to a considerable extent (PI. IX, fig. 16). Frequent 

 irregularities in the arrangement of the cells are produced 

 thereby, especially in Lophocolea heterophylla. 



In the latter plant the growth of the teeth on those leaves 

 which are intermediate between the two-pointed lower leaves, 

 and the entire upper leaves, is caused by division of the 

 terminal cells by alternately-inclined septa, not by septa 

 parallel to one another. 



Jungermannia bicuspiclata, and the closely allied /. conni- 

 vens and J. divaricata, comport themselves, in the matter 

 of leaf-development, similarly to the Lophocolea?. In these 

 latter, however, the regularity of the arrangement of the 

 cells is much greater ; the cell-multiplication in the lower 



