430 ' BOTANICAL GAZETTE [JUNE 
among anomalous dicotyledons, in which the mestome bundles of 
the aerial stem are not arranged in concentric bands. It is strange 
to notice that Podophyllum has this feature in common with 
Diphylleia, Leontice, and various species of Papaver, Thalictrum, 
and Actza. 
A transverse section of the stem above ground shows a thin 
walled epidermis and a cortical parenchyma that passes over into 
the large pith, both of which consist of thin walled cells of 
nearly the same size. The mestome bundles form three irregular 
bands, the two inner ones being located in the pith, and repre- 
sent various stages of development. Very characteristic is the 
structure of the leptome, in which we notice no other elements 
than sieve tubes and their companion cells, while cribral paren- 
chyma is totally absent. In this respect Podophyllum agrees with 
the monocotyledons and the Ranunculaceze only among the 
dicotyledonous orders. The hadrome consists of a number of 
vessels arranged very close to each other, and a well developed 
cambium is noticeable between this part of the mestome bundle 
and the leptome. Stereome forms closed rings around the 
mestome bundles; it is especially thick walled on the leptome 
side. 
By comparing the structure of the stem above ground with 
that of the rhizome, the following divergences were observed : 
The mestome bundles form only a band, and that an almost reg- 
ular concentric one, with only a few small bundles lying outside 
in the cortex. The vessels are very thick walled. While the 
cortex and the pith show approximately the same development 
as in the aerial stem, the outer layers of the cortical parenchyma 
show a very pronounced thickening of the cell walls, like those 
of collenchyma. Sheaths of thin walled stereome surround the 
mestome bundles without forming connecting layers between 
them. 
The structure of the petioles of the stem leaves shows a very 
irregular distribution of the mestome bundles. There is here, ves 
in the aerial stem, an almost regular peripheral band, located in 
the cortex; but inside this, in the pith, the mestome bundles are 
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