386 BOTANICAL GAZETTE [DECEMBER 
hypodermal and continuous layers of collenchyma surround a broad 
thin-walled cortex, rich in chlorophyll, and with some aggregated 
crystals. No endodermis is developed, but a closed sheath of 
stereome surrounds a stele of collateral mestome strands as in the 
midrib of the blade. The pith is solid, not divided into septa. 
Examined just below the basal pair of leaflets, the petiole is 
hairy like the rhachilla, and shows the same structure, except that 
there are two thin collateral mestome strands located in the cortex, 
thus outside the stele, and in these the leptome is covered by a 
few layers of stereome; the pith is solid. 
COTYLEDONS 
Although completely subterranean, the epidermis of the cotyle- 
dons shows stomata, but relatively only a few, on both faces of the 
thick fleshy blade. The lateral cell walls are straight on both faces, 
and the lumen is about the same, or slightly wider on the ventral 
face. The mesophyll lacks palisade cells, and is composed of a 
large, thin-walled, compact parenchyma of roundish cells. All the 
mestome strands are single, collateral, surrounded by parenchyma 
sheaths, and are imbedded in the mesophyll. The leptome is 
generally much better represented than the hadrome, and no 
mechanical tissues are developed in these leaves. 
Juglans cinerea shows the same structure as J. nigra, with the 
only exception that the pericycle in the stem represents an almost 
closed sheath interspersed with large, thick-walled, and porous 
sclereids. The pith is discoid, and the diaphragms contain many 
aggregated crystals. The pointed hairs of the leaf are more abun- 
dant than in J. nigra, and occur mostly in clusters of two to eight on 
the dorsal face of the blade. 
Characteristic of Juglans and Carya is thus the ample represen- 
tation of mechanical tissues, as collenchyma, stereome, and libri- 
form. Of these the collenchyma occurs in the stem, the periphery 
of the cortex proper, and in the leaves as hypodermal strata on 
both faces of the midrib. The stereome occurs as a secondary 
tissue in the cortex of the root and stem, as well as pericyclic arches 
or, sometimes, forming a closed sheath, interspersed with sclereids 
