222 : BOTANICAL GAZETTE [MAY 
In a stolon, terminated by an over-wintering bud, I found the 
same structure as described above as characteristic of the main 
rhizome, the only difference being that the collenchyma was less 
thick-walled; that the cortex contained large deposits of starch; and 
that the central stele showed very prominently three arches of mestome 
(leptome, cambium, and hadrome) separated from each other by 
very broad rays of thin-walled parenchyma. While the hadrome 
in this stele was thus confined to three arches of collateral mestome 
strands, the leptome was developed as isolated groups inside the 
endodermis, not only oustide the hadromatic rays, but also between 
them. 
While thus the peripheral steles of the main rhizome and the 
stolons show an almost equal development of collateral mestome strands 
around a central pith, the stele in the center shows the hadrome more 
or less distinctly combined in arches (two or three), while the leptome 
follows the entire periphery inside the endodermis (fig. 14). 
A corresponding structure is to be found in the aerial shoot which 
bears the long, narrow leaves and the inflorescences. In the apical 
internodes, for instance, we find the same tissues and arranged in 
the same manner, but the change of medium naturally brings about 
certain modifications of structure. In the rhizome and in the sub- 
merged portion of the ascending shoots the cortex does not reach the 
epidermis, but is completely inclosed by the collenchyma. In the 
aerial internodes, on the other hand, the cortex extends to the epi- 
dermis, thus breaking through the collenchyma, which here becomes 
developed as isolated strands, as prominent ridges; where the cortex 
reaches the epidermis it develops typical palisades, which contain 
much chlorophyll (fig. 21, C). 
The cuticle is very smooth and thin in the aerial internodes. 
The epidermis has stomata and glandular hairs, and contains cysto- 
liths. The collenchyma is very thick-walled and forms eight promi- 
nent strands of about ten layers; six of these strands correspond with 
the six peripheral steles, while the remaining two, which are some- 
what smaller than the others, are diametrically opposite each other 
and between two steles. The cortex is differentiated into one oF 
two strata of palisades, located in the furrows between the collenchy- 
matic ridges; the inner portion of the cortex contains less chlorophyll 
