Structure and Function of Endodermis in Abietinece 287 
IX. Cedrus IJbani Barrel. 
The endodermal layer consists of large regular cells with thick 
walls, the inner tangential walls being considerably thinner than the 
others (Fig. 9, d). No passage cells were found. Most of the inner 
tangential walls are unlignified; the outer tangential walls are of 
lignocellulose and have in addition patches of suberin on the inner 
surface. The radial and transverse walls consist of a thick inner layer 
of lignificd wall bordered on either side by a suberised layer, and the 
former are pitted at long intervals. 
One to two layers of hypodermal sclerenchyma are present, and 
the bundle is divided into two by a medullary ray. Numerous peri- 
cyclic elements are found with thick cellulose walls, while others are 
thinner and have lignified walls. Pitted tracheidal cells are also 
present. 
X. Tsuga canadensis Carr. 
' The endodermis of Tsuga resembles that of Abies in that it 
consists of large cells rather irregular in size (Fig. 12); the irregularity 
is more pronounced in Tsuga. The continuity of the endodermal 
sheath is interrupted by a single resin canal in the plane of symmetry. 
According to Daguillon the resin canal is absent from the cotyledon. 
There is on the whole rather slight development of thickening on 
the tangential walls. Most of the outer and some of the inner are 
unlignified. Neither tangential wall is suberised. The radial walls are 
composed of a core of lignocellulose with suberin on the surface. 
They are pitted at rather long intervals. The transverse walls resemble 
these in structure but are unpitted. Passage cells are found. The 
cells surrounding the resin canal are lignified, thus forming with the 
endodermis a continuous sheath of thickened cells. Only a single 
layer of hypodermal tissue is present, except by the resin canal, 
where a double layer occurs. The structure of the leaf is less xero- 
morphic than is the case for most of the species just described. 
XI. Pseudolarix Kcempferi Gord. 
The cells of the endodermis are very large in proportion to the 
size of the leaf, and have delicately thin walls resembling in this 
respect the other deciduous genus Larix. 
A considerable amount of lignification and suberisation takes 
place however, none of the walls being entirely soluble in sulphuric 
acid. Both inner and outer tangential walls are lignified and are 
suberised in patches. The radial and transverse walls have a thin 
