Isabel Soar 
284 
The radial and transverse walls have the same structure as in the 
species previously examined, only the former being pitted and usually 
at long intervals. On treatment with strong sulphuric acid parts of 
all the walls of some endodermal cells are dissolved, showing that in 
Fig. 9. (a) Pseudotsuga Douglasii Carr. Part of a transverse section of the leaf 
showing portions of the inner tangential walls unlignified. Outer tangential 
walls lignified, radial walls lignified and suberised. 
(b) Pseudotsuga Douglasii Carr. Part of a radial longitudinal section of 
the leaf. The outer tangential walls are lignified and pitted, the inner 
lignified in places, the transverse walls are lignified and suberised. 
(c) Larix europcea D.C. Part of a transverse section of a leaf showing 
the endodermis with portions of the inner tangential walls unlignified. 
(d) Cedrus Libani Barrel. Part of a transverse section of a leaf 
showing thick endodermal walls. Inner tangential walls unlignified in 
places. 
en., endodermis; per., pericycle; lig., lignocellulose; s., suberin; 
c., cellulose; c.per., thick cellulose walled elements of pericycle. ( x 240.) 
such cases a completely suberised layer is not present, even in the 
radial walls, and indicating the presence of passage cells. 
The endodermal walls are all very delicate, being considerably 
thinner than those of the species previously described; also the cells 
are larger in proportion to the size of the leaf. The pericyclic cells are 
