80 
F. 0. BOWER. 
observed, two of which are represented in figs. 2 and 3. In 
the former the square group of cells figured ocupied a central 
position, while the succession of segments was regular. In 
fig. 3 the succession of segments is as regular as in the former 
case, till the segment iv is reached ; then it appeared that 
a second segment (v) had been cut off from the same side 
of the apical cell as segment iv. The appearance of the 
walls as shown in the figure might suggest a possible interpre- 
tation of the meristem as being derived from four initial cells, 
as described by Schwendener in the roots of the Marattiacese; 
a careful examination of the section precludes this idea. It is 
further to be observed that the section represented in fig. 3, 
passed through the apical cell with its segments, while it also 
included a segment (already divided into four cells by walls 
disposed crosswise, and here shown by dotted lines) which goes 
to form part of the root-cap : this may be observed by focussing 
deeply into the section. Such sections, when used with proper 
precautions, are of great value, as preventing the possibility of 
mistaking cells below the apical cell, or group of initial cells, 
for the apical or initial cells themselves. 
Occasionally intermediate examples are found between the 
type with a single well-marked apical cell, and more complex 
arrangements. In the sections represented in figs. 4 and 5, 
neither the position of that cell which is probably the single 
apical cell, nor the arrangement of the tissue round it, give 
evidence of the growth having been strictly according to rule. 
Thus in the case represented in fig. 4, the three-sided cell 
marked (x) does not hold a central position in the section, and 
it is of relatively small size : here the appearance of the tissue, 
and the arrangement of the surrounding cells, suggest rather 
that the four-sided cell marked (x) has performed the function 
of an initial cell. Another example of irregularity is shown 
in fig. 5, b. The cells marked (x) hold a central position, and 
appear to be sister cells ; the surrounding tissue does not point 
to any definite regularity of succession of segments cut off 
from them. 
Of all the modes of arrangement of the cells of the apical 
