APEX OF THE ROOT IN OSMUNDA AND TODEA. 
97 
omitted by Haberlaudt in his ‘ Physiologische Pflauzen- 
Anatomie’ (p. 45). This type might be intercalated between 
that in the stem of Selaginella Wallichii and that of the 
roots of the Marattiaceae. 
It has already been pointed out in connection with the 
Marattiaceous type of structure of the root that a necessary 
consequence of a coaxial but not confocal system of periclinal 
curves is that some of them at least must stop short if the root 
is to maintain its cylindrical form. A careful observation of 
median longitudinal sections of both Osmund a and Todea 
shows that a more or less abrupt termination of periclinal 
curves in a posterior direction, such as may be readily observed 
in root-caps, is to be found in these roots, not only in the root- 
cap but also in the tissues of the body of the root. Fig. 35, 
a and b, show examples from the cortex of Osmunda and 
Todea. In the former case, taken from the same root as 
appears in fig. 14, the arrangement of the cells strongly 
suggests that characteristic of the root-cap, that is a coaxial 
arrangement, no less than four periclinal curves terminating 
abruptly in a posterior direction within a comparatively short 
distance. In fig. b only one of the periclinal curves termi- 
nates within the short space represented. If further evidence 
be wanted, it may be found by referring to fig. 14, and observing 
that the anticlinals present a distinctly convex surface to the 
organic axis of the organ. 
It was shown that a second necessary consequence of the 
coaxial arrangement is that the pericambium at the limit of 
the procambial cylinder would not be traceable as a continuous 
1 aver up to the initial group. Observations of both Osmunda 
and Todea show that this is actually the case ; the pericam- 
bium originates, like the pseudo-epidermis of Tax us, from por- 
tions of successive layers of cells. It may here be again stated 
that it has not been possible to trace the epidermis as a con- 
tinuous layer up to the initial group, nor have I been able 
to connect the origin of the epidermis with any wall, which 
appears in a definite position in each successive segment, as 
can be done in the type described by Naegeli and Leitgeb. 
VOL. XXV. NEW SKR. 
G 
