88 
Edith Chick on Torreya Myristica. 
wards would seem to have a double origin, one portion corres¬ 
ponding to the strand ( nix .) which is directly inserted upon the 
root metaxylem, and the other seeming to belong more intimately 
to the cotyledon trace (px. in Figs. 10 and 11.). 
Thus Torreya does not fall into any of the cases of typical 
diagrammatic passage from root to stem. A possible explanation 
of the “ dying out ” of the root protoxylem is that the xylem 
connection between the root and the cotyledons was made at a time 
when, and in a region where, elongation had ceased and possibly 
growth in thickness was taking place. This would account for a 
region devoid of spiral and annular elements. 
The two seedlings examined for this transition gave practically 
identical results. Of the two it was easier to follow in the younger 
seedling (that from Kew), but in each there was a great quantity 
of secondary xylem present which increased the difficulty. 
Anatomical Structure of the Cotyledon. 
At the base of the petiole the protoxylem is central (fig. 11.). 
The more internal of its elements are much crushed and these can be 
traced down to the “ metaxylem ” strand nix, while other elements 
not crushed are in contact with the primary and secondary xylem 
of the bundle. At this level there is only a very occasional centri¬ 
petal xylem element, while similarly very rare transfusion-tissue 
elements are found on the flanks of the bundle. The amount of 
both increases very greatly as the bundle is traced upwards, until 
half way up we have a state of affairs which recalls that in the 
cotyledon of Ginkgo or Cephalotaxus. 
Before, however, this level is reached, the bundle changes in 
appearance somewhat, having in transverse section an approach to 
a kidney-shape (fig. 12), with crushed protoxylem in the concavity, 
and a certain amount both of centripetal xylem and transfusion- 
tissue present. 
The centripetal xylem attains its maximum development half 
way up the cotyledon, while the amount of transfusion-tissue goes 
on increasing, until finally, at the apex, it is the only vascular tissue 
left. 
PI. vii., figs. 4 and 5, shew respectively a transverse and a 
longitudinal section about the middle of the cotyledon. By 
combining the two, it will be seen that the xylem of the 
bundle is composed of the following:—Starting from the dorsal 
side, we have secondary tracheides which show the typical Taxinean 
