136 AMERICAN MIDLAND NATURALIST. 
by a little stereome on the hadrome-side. No crystals were observed 
in the blade of any of these leaves. 
In regard to the petiole which often exhibits a structure 
characteristic of certain species, when examined just beneath the 
leaf-blade, we find in our Vyssa a large stele composed of six 
mestome-strands of the same structure as those in the midrib. A 
cross-section of the petiole shows a hemicylindric outline; epidermis 
is hairy and very thickwalled with wrinkled cuticle on the vertical 
face, and there are several, about six, hypodermal layers of thick- 
walled parenchyma with the stele. In this parenchyma large 
single and aggregated, globose crystals of calcium oxalate are 
quite abundant, beside some few idioblasts, very conspicuous by 
their enormous size and stellate shape. There is no endodermis, 
but a stereomatic pericycle on the leptome-side of all the mestome- 
strands. The selereids, the peculiar, small glandular hairs and the 
mestome-strands being connected with epidermis, these characters 
together may be of taxonomic importance. In Cornus florida for 
instance * there are no glandular hairs, only long, bifurcate, and 
no sclereids; furthermore the lateral veins are embedded in the 
chlorenchyma. But otherwise so far as concerns the internal 
structure the Cornacee offer no well marked characters by which 
we might distinguish the genera or the species; on the other hand 
we must admit that our knowledge of this particular part of the 
structure is, at present rather limited, not speaking of the root- 
system and the seedling-stage with the primary leaves. To the 
diagnosis of the species JV. syfvatica should be added that the leaves 
of young specimens are frequently dentate like those of JV. aqua- 
tica Marsh. 
Fig. 1. Seedling of Nyssa penses Marsh. R, the primary root; H, the 
pocotyl; Cot., the two cotyledons; L!, L? and L?, the primary 
leaves; natural size. 
2 
m 
M 
One of the cotyledons, showing the venation; natural size. 
Fig. 3. Leaves ofa shoot from a shrub; two thirds of the natural size. 
Fig. 7. Leaffrom a shrub, showing the dentate margin; two-thirds of the 
natural size. 
Cross section of hypocotyl; C, cortex; End., endodermis;x496. 
Cross section of hypocotyl; Camb, cambium; L., leptome; the other 
letters as above; x496. 
c 
R R 
o 0 
* Aerial, nonfoliaceous cotyledons exist, but are evidently very rare; they 
occur in Jatropha (Bot. Gazette 1899 p. 60). 
