HICK : OA LAMOSTACHYS BINNEYANA. 
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three cariual canals, while the fifth has four. As the sections cannot 
have been far apart in the uncut strobilus, this would seem to show 
that the number of carinal canals, i.e., of primary vascular bundles, 
may vary in different parts of the axis. 
Secondary Xylem. 
Taking the carinal canals to be the representatives of the 
primary vascular bundles, fig. 1 shows that in some examples of 
Calamostachys Binneyana no secondary thickening is met with, 
though its subsequent appearance is not precluded. In others, how- 
ever, secondary xylem, composed of scalariform tracheids is met 
with, and there as in the stem of Arthropitys, the development 
begins at the carinal canals. Thus three w r edge-shaped masses are 
usually produced, whose elements spread out in radiating rows and 
in a fan-like manner from the carinal canals, while a little later 
intermediate xylem is developed in the intervening areas. In this 
way a narrow but complete zone of secondary xylem is formed. The 
three bands of intermediate xylem are usually convex towards the 
pith, which thus takes the triangular shape with concave sides so 
often noticed by previous writers. All this however has been so well 
described and illustrated by Williamson in his fifth* and tenthf 
Memoirs that it need not further detain us. 
The Cortical Tissues. 
The tissue which immediately surrounds the primary vascular 
bundles or the secondary xylem when such is present, is usually 
absent from the petrified strobili, and only one section has been pub- 
lished in which it is preserved. This we owe to Williamson, who in 
his account of it tells us+ that "the vascular axis is closely sur- 
rounded by a dense cellular layer," which "passes into a more 
open and delicate cellular tissue in which there are large lacunae 
. . . probably due to partial desiccation." Fig. 1, PI. I., repre- 
sents a section in which the cortical tissues apparently still retain 
their original form unchanged, In it the inner parenchyma (i.p.) is 
seen to be composed of cells of relatively large size, with delicate 
* Op. cit., Pt. v., 1871, p. 72, fig. 38. f Op. cit., Pt. x., 18S0, p. 504, fig. 16. 
J Op. cit., Pt. x'., 1880, p. 503. 
