14 ROYAL SOCIETY OF CANADA 
The phloem on its inner face consists of several rows of thin-walled 
elements which contain very prominent nuclei. (Plate VI, fig. 11.) This 
tissue is succeeded by a well-defined layer of sieve cells which are rather 
thick-walled and remarkable, not only for their radial compression, but 
also for the contortion of the walls, features which are also found in 0. 
cinnamomea, and, to less marked extent, in Todea, but do not appear in 
the fossil. (Plate VI. figs. 11 and 12.) Opposite the medullary rays 
the sieve cell tissue broadens radially to form blunt, wedge-shaped 
masses which project into the ends of the rays after the manner des- 
cribed by De Bary.! (Plate VI. fig. 11.) The outer phloem consists 
of several rows of thin-walled elements containing prominent nuclei. 
They are somewhat elongated tangentially (Plate VI., fig. 11), but 
probably not to the extent to be inferred from De Bary’s statement.? 
Endodermis.—In Osmunda regalis there is a well-defined endoder- 
mal layer which is also present in O. cinnamomea, but lacking in the 
fossil. It consists of a layer of dark coloured cells which he in one or 
two rows, or locally of three or four rows. The cells are hexagonal and 
elongated tangentially, but not infrequently they assume a distinctly 
oval form and become somewhat thicker walled. (Plate VI., fig. 11.) 
Parenchyma Zone.—Immediately external to the endodermis is a 
broad zone of parenchyma having a thickness of about 1 mm., and an 
external diameter of 4°5 mm., constituting the inner cortex. In ©. 
cinnamomea these dimensions are somewhat greater, being 1°25 mm. 
and 5-5 mm. respectively. (Fig. 2.) The tissue throughout is colour- 
less. The cells are rather large and thin-walled. They contain very 
prominent nuclei and are always filled with starch. (Plate VI, fig. 11.) 
This region is traversed by few leaf traces, which are in the form of an 
open crescent, and in this respect it approaches the type found in the 
fossil much more nearly than does O. cinnamomea. ‘This region is 
exactly represented in the fossil by the third region described. (Plate 
Tite 2.) 
Sclerenchyma Zone.—Following the parenchyma is a dense, dark 
coloured zone of sclerenchyma forming the external cortical region of 
the stem proper. (Fig. 2.) This zone is represented in the fossil by 
remnants only (Fig. 1), and in the microscopical preparation, only very 
small fragments appear (Plate I., fig. 2.) While in the fossil the 
limits of this zone cannot be determined, its relative volume may be 
inferred by comparison with Osmunda. In O. regalis it has a thickness 
of about 2 mm. and an external diameter of 8°5 mm., while in O. 
cinnamomea, with about the same average thickness, it has an external 
diameter of 9 mm. If, then, the same ratio obtains for this as for the 

1 Comp. Anat. of Phan. & Ferns, 347. 
2 Comp. Anat. of Phan. & Ferns, 347. 
