THE HIGHER CRYPTOGAMIA. 237 



ensues takes place, if not exclusively, at all events prin- 

 cipally, in a direction at right angles to the septum last 

 produced. This septum which, at the instant of one divi- 

 sion, forms one of the sides of the isosceles triangle repre- 

 sented by the upper surface of the cell of the first degree, 

 is, until the next division, far surpassed in longitudinal 

 growth by the two other side walls of the apical cell, so 

 that the latter then constitute the sides and the newly- 

 formed septum the base of the triangle. The new division 

 is produced by a septum which is parallel to the second 

 side wall of the apical cell, which side-wall at the time of 

 the preceding division was the longer one, and which in the 

 mean time has become elongated and displaced. 



The diagram given in PL XXXII, fig. 5, of the mode of 

 succession of four such divisions of the apical cell of a bud 

 with the /a arrangement, will explain the above sugges- 

 tion. 



The triangle enclosed by the lines 1, 2, 3, represents 

 the apical cell before the first of these divisions ; the line 4 

 represents the course of the dividing membrane. This 

 cell (which we will designate with the figure II until the 

 next division) now expands to the left : the line 4 now be- 

 comes the base of the triangle ; the line 1, increased by the 

 line l n becomes one side of the triangle, and the line 3, 

 displaced to 3 11 and lengthened, becomes the other side of 

 the triangle. The next division is represented by the 

 line 5. This line becomes the base of the upper surface 

 of the cell, which is enclosed by the lines 3 n , 4, and 5, and 

 which expands again to the left. By this expansion the 

 line 3 becomes the line 3 m , and the line 4 becomes 4 m . 

 The line 6 represents the third division. The apical cell is 

 now first bounded by the lines 4, 5, 6. By a fresh expan- 

 sion of the cell the line 5 is increased by the line 5 1V , 4 is 

 shifted to 4 1V , 2 to 2 IV , and 1 is extended to 1 IV . 



PI. XXXII, fig. 6, exhibits the somewhat complicated 

 mode of arrangement and displacement of the cells of the 

 second degree after three more such divisions of the apical 

 cell. 



All the above facts can easily be brought under the one 

 point of view of the above supposition. The latter explains 



