THE HIGHER CRYPTOGAMIA. 25 



by a transverse septum. The body thus formed, of which 

 the ground plan exhibits five cells, now protrudes into the 

 indentation of the fore edge (PL IV, fig. 17). The further 

 multiplication of its cells in the superficial direction takes 

 place, in the following manner : a membrane, directed 

 obliquely outwards, is mounted upon each of the last-formed 

 transverse septa ; thereupon each of the inner ones of the 

 four newly formed cells of the fore edge divides by a trans- 

 verse septum at right angles to the longitudinal axis of the 

 shoot. In each of the outer cells there is formed, at the 

 same time, a longitudinal septum parallel to the last-formed 

 oblique septum. By this means the ground is laid for the 

 fan-shaped arrangement of the cells of the middle shoot. 



All that is now necessary for the development of the cell- 

 arrangement of the half-developed (PL IV, fig. 23) as well 

 as of the perfect middle shoot, is the repetition of the 

 division by transverse septa of the two middle cells of the 

 fore edge — the repeated transverse division of the cells late- 

 rally adjoining the latter- — the commencement of a longitu- 

 dinal division in these cells after a repetition once or twice of 

 the transverse division, and lastly, — the frequent recurrence 

 of the same series of divisions in the lateral cells for the 

 time being of the fore edge of the shoot. 



The growth of the middle shoot of the germ-plant is 

 limited, as is the case with all the divisions of the stem in 

 Pellia. The multiplication of its lateral cells is slight at the 

 base, increases to the middle, and increases rapidly from 

 thence to the apex. The form of the shoot is therefore 

 either that of a short spatula, or semi-oval. 



The cells which are situated in the axil formed by the 

 middle shoot and the lateral wing of the germ-plant begin 

 to multiply vigorously, according to a similar rule, as soon as 

 that shoot has attained to about a fifth part of its develop- 

 ment. The cell, which, when seen in profile or from above or 

 below, is oblong or trapezoid, appears, when viewed in the 

 direction of the surface of the plant, divided in the first in- 

 stance, by means of a transverse septum, into two cells, of 

 which the hinder cell is square, and the front cell trapezoid. 

 The latter divides by a longitudinal septum ; each of the 

 newly formed ones again by a transverse septum ; the outer 



