AMERICAN MIDLAND NATURALIST. 135 
mature leaves of the tree, since the mestome-strands (about seven) 
are arranged in a plane instead of in a stele. If we examine the 
primary leaves (L'—Ij in figure 1) we notice exactly the same 
structure of epidermis as to lumen and shape as described under 
the cotyledons. These primary leaves, however, are hairy, and the 
veins show the same simple structure as observed in the cotyledons. . 
No crystals were found and no idioblasts either, although such 
occur in the petiole of the same shape as in the final leaves. 
The foliar structure characteristic of the species is, however, 
the one possessed by the leaves of the mature tree. These are 
during the summer held in a horizontal position, and their structure 
is bifacial with stomata confined to the dorsal face, and with a 
ventral palisade-tissue. ^ Very distinct cuticular striations are 
noticeable on both faces of the blade, but only the dorsal is hairy 
, With small glandular (Fig. 14), and very long pointed hairs (Fig. 
13), unicellular in both. "The stomata (Fig. 12) have, sometimes, 
subsidiary cells parallel with the stoma, but are much smaller than 
those of the cotyledons and primary leaves. As already mentioned 
the lateral cell-walls of epidermis are nearly straight (Fig. 12), and 
the outer is thinwalled except beneath the midrib. The palisade 
cells represent a single layer, and are very high (Figs. 15 and 16), 
covering a few (about six) strata of irregularly branched cells 
constituting a pneumatic tissue with very wide intercellular spaces, 
which are especially noticeable in superficial sections (Fig. 11). 
We find in the chlorenchyma numerous idioblasts (Fig. 15), very 
thickwalled and porous representing the so-called sclereids. "These 
peculiar cells are known, furthermore, from species of Garrya and 
Griselinia, and they show translucent dots when the leaf is 
held towards the light. The midrib has a dorsal keel with 
hypodermal collenchyma and a large tissue of thinwalled, colorless 
parenchyma, but lacks endodermis ; there is, on the other hand, a 
thickwalled stereomatic pericycle covering the leptome-side of the 
two separate mestome-strands which constitute the midrib. h 
two strands turn their leptome towards the surface of the blade, 
thus the hadrome is in the centre enclosing a small pith. Of these 
the dorsal strand is the larger; it is crescent-shaped (in cross- 
section) and contains leptome, cambium and relatively long rays of 
vessels. All the other veins are provided with distinct parenchyma- 
sheaths (P. S. in fig. 16) and are connected with both epidermes 
by strata of thin-walled parenchyma ; they are frequently supported 
