228 
RUTH HOLDEN 
access to material from a number of different localities, some of which 
was identified by Eaton himself, it seems as though the error must be 
his. Figure ii shows these structures in E. hiemale. According to 
Eaton, Duval Jouve, and Milde, the carinal bast in this species is the 
better developed, and interrupts the green parenchyma under the 
ridges, while it is continuous under the furrows. If figure ii be 
examined with a hand lens, however, it will be found that while the 
masses of bast fibers at the ridges are larger than those at the furrows, 
there are invariably, as in E. variegatum var. Jesupi, cells extending in- 
ward from the latter which cut across the palisade tissue at that point, 
also. Figure 12 shows a small portion at a higher magnification, and 
there can be no doubt that such is the case. This section was cut from 
material grown in Toronto, Ont. On the other hand, plants grown in 
Cambridge, Mass., presented usually the conditions which have been 
described as typical for the genus — the parenchyma is continuous 
under the furrows.^ The importance of these discrepancies is not 
necessarily great, Milde himself having found considerable variation 
throughout the genus, and especially in E. hiemale. 
With this description of the aerial stems of the three Equiseta, it 
is clear that E. variegatum var. Jesupi occupies a position somewhat 
intermediate between the other two. Its bluntly biangled ridges are 
half way between the rounded ones of E. hiemale and the sharply 
angled ones of E. variegatum; while in the distribution of bast fibers 
and green parenchyma, it has the vallecular interruptions common to 
both the others, and the carinal interruptions of E. hiemale. 
In the structure of the rhizome, there is also considerable divergence 
among the three. Figures 13, 15 and 17 represent respectively trans- 
verse sections of the internode of the rhizomes of E. variegatum, E. 
variegatum var. Jesupi, and E. hiemale. As in the aerial stems, the cen- 
tral canal of E. hiemale is much larger in proportion to the vallecular, 
than is the case with either of the others. The endodermis of E. varie- 
gatum has the same distribution in the underground as in the aerial 
stem — it is double, and continuous internally and externally. The en- 
dodermis of E. hiemale, on the other hand, is like that of E. variegatum 
in the aerial stem, but in the rootstock, it forms a separate sheath 
- Since writing the above, I have had an opportunity of investigating the stems 
of E. hiemale from Niagara Falls, Canada, and from the Cambridge, England, 
Botanical Gardens, and in all the specimens have found the green parenchyma con- 
tinuous, under the furrows. 
