92 
F. 0. BOWER. 
rupted series of confocal paraboloidal surfaces, their common 
focus being situated in the apical cell itself. The periclinal 
walls in the root-cap, in accordance with Sach’s demonstration, 
constitute a series of similar curves, which are, however, not 
confocal, but are coaxial. Since the anticlinal walls cut the 
periclinals at right angles, those in the body of the root, which 
cut the confocal curves, present a concave surface to the axis 
of growth, while those in the root-cap, cutting the coaxial 
curves, present a convex surface (compare Sachs, 1. c., Taf. iv, 
fig. 11). 
In the second type, according to the description given by 
Schwendener, the arrangement differs from the above type in 
certain important points, and a diagram may be drawn to show 
the scheme of construction as in fig. 34. In this type of 
structure there are in the first place walls in two radial planes, 
which cut one another at right angles, and their line of inter- 
section is the organic axis of the root. The periclinal walls 
are none of them confocal, neither those which lie in the body 
of the root, nor even those in the procambial cylinder ; they 
are, however, all coaxial, and their common axis is the line of 
intersection of the radial walls, that is the organic axis. It 
will be obvious that the periclinals are necessarily not confocal 
in those organs where the apical cell (or the group of initial 
cells) has the form of an inverted truncated pyramid, and gives 
off segments from the truncated apex of the pyramid (the 
lower end), which take part in the formation of the body of 
the organ. 1 The apparently transverse walls by which succes- 
1 In Sachs’s ‘ Vorlesungen,’ p. 556, the following passage is to be found 
immediately succeeding an allusion to the apex of the root in the Marattiaceae : 
“ Dagegen ist hervorzuheben, dass Scheitelzellen iiberhaupt nur dann im herge- 
brachten Sinne moglich sind, wenn die Peri- und Antiklinen confokale Cur- 
venschaaren darstellen oder kurz bei confokal gebauten Yegetationspunkten. 
Ist der Vegetationspunkt dagegen mit facherformig verlaufenden Antiklinen 
durchzogen, ist die Volumenzunahme gegeu den Scbeitel bin am grossten, wie 
oben bei fig. 288 gezeigt wurde, dann konnte man unter Umstanden wohl 
auch noch in erweitertem Sinne Scheitelzellen annehmen, allein die Schrift- 
steller haben in diesen Fallen iiberhaupt nicht von Sheitelzellen geredet, und so 
konnen auch wir davon absehen.” In the scheme here constructed for the 
