T40 MORPHOLOGY OF TISSUES. 
last is again immediately broken up by a septum //*) into two disc-shaped 
cells, and in each of these numerous small cells arise by the formation of vertical 
and afterwards horizontal walls (as may be seen in the figure further back from 
the apex) ; and it is easily seen how the whole branch is built up of portions 
of tissue, each of which originated from a single segment. The same takes place 
Fig. 109.— Apical region of a slioot oi Met.zgeria furcata in the act of bifurcation, looked at from the surface (after Kny). 
The shoots consist of a single layer of cells ^ff), which is however penetrated by a mid-rib n three to six layers in 
thickness. 
in the lateral branchlets y, which in this case arise originally from lateral 
protuberances of the apical cell. These processes are remarkably clearly seen 
in Sh'pocau/on, in the first place because only one row of segments is formed 
lying one over another, and in the second place because the segments themselves 
are transformed into portions of tissue without at the same time growing, as is 
FIG. no.— Diagrammatic representation of the segmentation of the apical cell, and of the first divisions in the segment of 
Metzgeria furcata (after Kny). A apex seen from the surface; B the same in vertical longitudinal section; C an apex in the 
act of bifurcation ; a new apical cell is formed in the third-youngest segment. 
usually the case. Distortions often occur from the growth of the segments, which 
render difficult an investigation of the processes of division. 
Figs. 109 and 110 show us a case in which the apical cell is divided alternately 
right and left by oblique walls, so as to produce two rows of segments attached 
to one another in a zigzag manner within and behind, but separated to some 
