106 HOFMEISTElt, ON 



soon divided by a septum at right angles to the longitu- 

 dinal line of the bud. The latter cell, after previous trans- 

 verse expansion, divides by a septum parallel to the chord 

 of the arc represented by that portion of the margin of 

 the bud to which the cell in question belongs. The outer 

 ones of the newly formed cells then divide by septa at 

 right angles with the last-formed septum (PI. XV, figs. 

 3 5 ; and compare Nageli's excellent account of this pro- 

 cess, 'Zeitschr. f. Bot.,' Hft. 2, S. 150). The further in- 

 crease in the cells of the bud is caused by the growth of 

 septa in the cells of its fore edge alternately at right angles 

 or parallel to its margin, and by the formation of septa 

 parallel to the margin in the cells of the edge of its lower 

 part. The increase in breadth of the apex exceeds, at an 

 early period, that of the base (PI. XV, figs. 3, 4). 



The longitudinal growth of the bud is limited, as is the 

 case with all the shoots of the Marchantiese. When it 

 is finished a very considerable increase in the breadth of 

 the lower part of the bud commences. Here the marginal 

 cells divide repeatedly by septa parallel to the margin, 

 alternating with radial septa. The marginal cells also of 

 the upper part, with the exception of those of the apex, 

 multiply in like manner, although less actively ; they are 

 soon overtaken by those of the lower part. The cells, 

 however, of those two places on the lateral margins at which, 

 at an earlier period, the upper, wider half of the bud 

 separated itself from the low T er, narrower portion, take no 

 part whatever in this multiplication (PL XV, fig. 7), and 

 as little also in the important expansion in length and 

 breadth which occurs shortly afterwards in the remaining 

 cells of the buds. In this way two very deep, lateral in- 

 dentations are produced in the middle of the buds, the inner- 

 most space of which indentations is occupied by a group 

 of small cells, with a trapezoidal basal outline (PI. XV, 

 figs. 7, 8). At the time when as many as ten cells can be 

 counted in the longitudinal line of the bud, this group 

 appears as a single layer of cells. Then, for the first time, 

 it begins to grow in thickness ; in the first place, by the 

 division of the cells of the middle region by horizontal 

 septa (PI. XV, fig. 1*). For a still longer period the Ion- 



