1921] HOLM—CARYA AND JUGLANS 379 
is quite thick-walled. The cortex is differentiated into a peripheral 
sheath of collenchyma, three or four strata, and an interior of 
thin-walled parenchyma, five to six layers. Rhombic crystals of 
calcium oxalate were observed in the collenchyma, while aggregated 
crystals occurred sparingly in the inner part of the cortex. The 
phellogen arises in the hypodermal stratum of the collenchyma. 
A thin-walled, starch-bearing endodermis surrounds a band of 
small isolated strands of stereome, separated from each other by 
natrow rays of parenchyma. The stele shows a continuous zone of 
leptome, cambium, and hadrome in deep rays, accompanied by 
many layers of libriform. A homogeneous, slightly thick-walled 
pith, destitute of starch, occupies the central portion of the stele; 
the pith is not septate. 
In branches of the mature tree the cork appears in many 
thin-walled strata; the stereome is well represented as several, 
until seven, concentric bands of isolated strands, the result of one 
season’s growth. Large rhombic crystals abound in the leptome, 
and the hadrome is divided by broad tangential bands of moderately 
thickened libriform. The very thick-walled, porous vessels so 
characteristic of J uglans do not occur in Carya, and the pith is 
nowhere septate. 
LEAF 
Viewed in superficial sections the ventral epidermis shows the 
lateral cell walls prominently undulate, hairs and stomata being 
absent. In the dorsal epidermis the lateral walls are less undulate, 
but stomata and hairs are abundant; of these the former are all 
of the same size, and surrounded by four to seven ordinary epider- 
mis cells; the hairs are of the same types as observed upon the stem. 
Viewed in transverse sections the cuticle is thick and smooth 
on both faces of the leaf blade, and the outer cell wall of epidermis 
is thickened. Large oil drops abound in the ventral epidermis. The 
mesophyll consists of a typical palisade tissue of one stratum, cover- 
ing a very open pneumatic tissue of three to five layers. Numerous 
large cells containing aggregated crystals are’ scattered in the 
palisade tissue, while single rhombic crystals abound in the pneu- 
matic tissue, especially close to the veins. 
