1921] HOLM—CARYA AND JUGLANS 385 
as a closed sheath. Bordering on the stereome is a broad zone of 
thin-walled parenchyma, with narrow isolated strands of leptome. 
The cambium forms a closed ring, and the hadrome is in deep rays 
with much thick-walled libriform. The pith is homogeneous, 
thin-walled, filled with starch, but solid, not septate as in the shoots 
of the mature tree. 
LEAF 
When unfolding, the leaves are very hairy, especially on the 
dorsal face, and the hairs are of the types that occur on the young 
shoots. The stomata are confined to the dorsal face, and lack 
subsidiary cells. They represent two sizes, both of which are 
equally common. Viewed in superficial sections the lateral walls 
of epidermis are straight om both faces of the leaf blade. With 
regard to the distribution of the various hairs, the pointed, fascicu- 
late, abound beneath the veins, and are absent from the ventral 
face; the glandular are common on both faces; but the largest 
type, sessile with a large head, are confined to above and below 
the mesophyll. The mesophyll consists of a compact palisade 
tissue of a single stratum, or sometimes two strata (fig. 18, P), 
covering a very open pneumatic tissue with numerous large cells 
containing aggregated crystals, especially close to the epidermis. 
The midrib is supported by several hypodermal layers of 
collenchyma on both faces, and is furthermore surrounded by a 
water-storage tissue. There is no endodermis, but a closed sheath 
of thick-walled stereome’ in several strata surrounding the steloid 
midvein, which is composed of an obtusely triangular band (in 
cross-sections) of collateral mestome strands inclosing a central 
parenchyma, a pith. In these mestome strands the hadrome 
faces the pith, while the leptome turns toward the periphery, even 
in the ventral part of the stele. Characteristic of the hadrome is 
the abundance of thin-walled parenchyma in continuation with the 
vessels. The lateral veins contain only single mestome strands 
which are supported by stereome extending to the ventral and 
dorsal epidermis, broken on the sides by thin-walled cells of a 
parenchyma sheath. 
Between the leaflets the rhachilla is hemicylindric (in cross- 
sections), very hairy, with long stalked glandular hairs. Several 
