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RUTH HOLDEN 
E. scirpoides Michx., E. laevigatum A. Br., and E. rohustum A. Br. are 
all connected by transitional forms, they should be considered a single 
species. It may be possible to introduce some order into this chaos by 
a more careful anatomical study of these forms. As a possible first 
step in this direction, E. variegatum var. Jesupi A. A. Eaton has been 
chosen. 
This variety was originally described by Eaton as "almost exactly 
intermediate between E. variegatum and E. hiemale,'' and the photo- 
graphs of plate I show such to be the case. Figures i, 3 and 5 re- 
present respectively E. variegatum, E. hiemale, and E. variegatum var. 
Jesupi; figures 2, 4, and 6 the same at double the magnification. In 
size of stem and cone, the variety is approximately half way between 
E. variegatum and E. hiemale. According to Mr. Eaton, one of the 
best diagnostic characters is that of the sheath. In E. variegatum, 
it is loose, terminating above in persistent teeth (fig. 2). These teeth 
have a dark median groove, with a white border on each side, and end 
in deciduous awn like points. The sheath of E. hiemale on the other 
hand, is tight, with a black base and tip. The teeth are long, but 
articulated to the sheath and soon deciduous (fig. 4). The sheath of 
E. variegatum var. Jesupi is usually loose as in E. variegatum; like 
E. hiemale it has a black band, which in the second year reaches the 
base, while the upper part becomes ashy (fig. 6). The teeth are similar 
to those of E. variegatum, having the same dark median groove, and 
white border. Unlike E. variegatum, however, the awn points are 
usually persistent. Another fairly constant feature is the character 
of the ridges. This may be seen more easily in transverse sections, 
but it is indicated in the habit photographs. In E. variegatum^, they 
are sharply biangulate, with a groove down the center of each. There 
is accordingly, a double row of siliceous tubercles to each ridge. 
Those of E. hiemale var. affine, on the other hand, are rounded, with a 
single row of tubercles. They may be clearly seen in figure 4. In E. 
variegatum var. Jesupi, the ridges are usually bluntly biangular, with 
rarely a carinal furrow. Like E. variegatum, there is usually a double 
row of tubercles (fig. 6). 
With this brief account of the external appearance of these three 
Equiseta, we may turn to their internal structure. Figures 7, 9, and 
1 1 represent respectively transverse sections of the internode of the 
aerial stems of E. variegatum, E. variegatum var. Jesupi, and E. hiemale. 
In some respects they are quite similar; all have a double endodermis 
