3 1 6 Bower . — The comparative examination of the 
of this it follows that the anticlinal curves all present a 
convex surface to the axis of growth, there being no dis- 
tinction in this respect between the root-cap and the body of 
the root. In fact the construction of the root is throughout 
on the coaxial or fan-like plan distinguished by Sachs 1 . It 
is further to be noted in connection with the scheme repre- 
sented in Fig. 1 7, that the apparently transverse walls, by 
which successive segments are cut off from the lower ends of 
the truncated pyramidal initial cells, form part of the series of 
periclinal curves ; and that the focus of each successive peri- 
clinal, by which segments are cut off from the initial cells to 
form the body of the root, lies at the time of segmentation at a 
point below the group of initial cells. In the former type, how- 
ever (Fig. i), it will be readily seen that the focus or centre 
of construction lies in the apical cell itself (Sachs, 1 . c.). Thus 
in passing from the first to the second type of construction, 
there is a sinking or lowering of the centre of construction ; 
since the anticlinals cut the periclinal curves at right angles, it 
follows that where the centre of construction is more de- 
pressed, the sides of the apical cell or of the initial cells will 
be less inclined to one another, and more nearly parallel than 
is the case where the focus lies at a higher point, for instance 
in the apical cell itself. The figures of Schwendener clearly 
demonstrate that this is actually the case in the Marattiaceae, 
in which the initial cells appear almost oblong in longitudinal 
section. Lastly, it is clear that in our second type the four 
initial cells may be represented to the mind as being gaps 
in the system of construction in just the same sense as the 
idea is applied by Sachs to the single apical cell. 
If now the observations above detailed for the roots of the 
Osmundaceae be compared with the two types of construction 
thus defined, it will be clearly seen that though subject to 
considerable variation of detail, they occupy an intermediate 
position between the two types : thus a single initial cell is 
but rarely found, the number being variable up to four, which 
seems to be the usual number for Todea ; the sides of the 
1 Lectures, Engl, ed., p. 451. 
