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THE AMERICAN MIDLAND NATURALIST 81 
parenchymatous cells rich in chlorophyll and with no intercel- 
lular spaces. The chlorophyll is confined mainly to the periphery. 
The centrally placed fibrovascular bundle is of the collateral 
type with the hadrome facing the upper or ventral face and the 
leptome pointing toward the lower or dorsal face. 
On either side of the main fibrovascular bundle close to the 
lateral margins of the petiole and along the same plane are situated, 
among the parenchyma cells two strands of incomplete wood- 
bundles (Fig. 9 Vs.). 
The cotyledons themselves (Fig. 1o-11) in structure are of 
the bifacial type. In cross section the internal ground-tissue 
(mesophyJl) is composed of thin-walled parenchyma cells of dif- 
ferent outline. Just under the upper epidermis (Ep.) there are 
two rows of more or less elongated cylindrical cells which form a 
rather compact palisade-tissue; while the cells of the spongy 
parenchyma, filling the lower half of the ground-tissue, are less 
regular as to shape and arrangement. Due to this irrevularity 
the intercellular spaces are much larger in the spongy tissue than 
they are in the palisade tissue, but there is, nevertheless, free 
passage from the lower to the upper epidermis. All the cells of 
the ground-tissue are rich in chlorophyll. In the fibrovascular 
bundles the hadrome (Had.) is placed superiorly next to the pali- 
sade tissue with respect to the underlying contiguous leptome 
(Lep.) next to the spongy parenchyma. The epidermis is com- 
posed of thin-walled cells in which different stages of formation - 
of stomata may be observed communicating, when fully developed, 
with the chlorenchyma by intercellular spaces. (Ep.—Ep’., the 
former the upper the latter the lower epidermis). A surface view 
of the epidermis (Fig. 11) shows cells containing many proto- 
plasmic granules confined close to the walls. The elliptical stomata 
average about 630 & distant from one another, and the struciure 
of the upper face differs in no essential way from that of the lower. 
The epidermal cells in surface view range from 315-540 {4 in width 
and from 630-1008 u in length. 
Tue Epicoty,. (Fig. 12). 
The fibrovascular structure (mestome) of the epicotyl presents 
characters different fr6m those of the hypocotyl. The mestome is 
arranged into four, more or less, separate strands of no definite 
shape with secondary meristem occupying the position between 
