382 Bower . — The comparative examination of the 
of greatest curvature, or margins, are subject to various deve- 
lopment in different parts, and are the seat of the branchings 
of a higher order. 
The meristems of the various parts having been investigated 
in a series of plants which bridges over the transition from 
growth with a single initial to growth with several, it is to 
be expected that some light may have been thrown upon the 
problem of the real nature of the apical cell, and of the causes 
which bring about so remarkable a construction as that where 
there is a regular segmentation from an initial of definite 
form. Though the solution of the problem is not yet to 
hand, certain interesting conclusions may be drawn from a 
comparison of the plants studied 1 . 
The comparison of Figs. 3 and 4 of roots, and of Figs. 39 
and 43 of leaves, shows, in place of a single three-sided initial, 
three initials so arranged, together with their segments, as to 
correspond to what is seen in transverse section through seg- 
ments immediately below a typical three-sided apical cell. 
Thus both in certain roots and in certain leaves there may be 
seen a construction which is the equivalent of the continuation 
of the typical system of construction upwards into that space 
(the apical cell), which is usually unsegmented. This I take 
to be evidence supporting the view of Sachs that the apical 
cell is but a gap in the system of construction : though in 
other cases (Figs. 12, 25, 27, 28) the arrangement of the walls 
is not according to the exact type, still I think the conclusion 
is justified that the difference between growth with one initial 
and with several initials is due to the greater completeness in 
the latter case of the system of walls. 
It is obvious that not only the apex of the average root, 
but also those of stem and leaf are more bulky in the higher 
terms of our series than in the more slender, lower terms : 
1 Sachs, in his well-known paper { Ueber Zellanordnung und Wachsthum ’ 
(Arbeiten, Vol. II, p. 200), writes in connection with the partitioning off of the 
interior of plants by cell-divisions and its relation to growth as follows : — { The 
acquisition of a cellular character of the interior is accordingly an independent 
phenomenon, the cause of which we are as little aware of as that of growth itself : 
but from what has been said, it must necessarily be subordinated to growth.’ 
