r042 General Notes, [October i 
section of a mature leaf be obtained, the two pairs of cellsen 
be seen, one above the other (Fig. 2, æa, upper pair of guad 
cells; ġġ, lower pair). 
With reference to the distribution of the stomata, Sachs 
the general statement that in the genus Equisetum they ae 
always found in the furrows and never on the ridges; but £ 
arvense seems to be a partial exception to this rule, as upon the 
leaves the stomata are invariably on the ridges. 
Taking the fertile plant, we find the leaves arranged in sheaths 
at the nodes of the stem; these sheaths are entire at the base but 
broken at the top into numerous teeth, which begin to divergeia 
the deeper furrows (Fig. 4 ee). Fig. 4 shows an outline section 
of a leaf taken about half way up; the upper surface is the outer 
one, on which the stomata are always located. It will be seen 
the leaf where they are most abundant. Where the leaves jot 
the stem the furrows, ¢ e, are continued (Fig. 5 ¢¢), the furrow # 
disappears, becoming continuous with the highest part of the 
ridge of the stem (Fig. 5 m). Fig. 5 is a section of one of the 
ridges of a stem; aa are the cells containing chlorophyll; whee 
these touch the epidermis there is a slight elevation 
general slope, and on these places the stomata occur. 
The distribution of stomata on the stem and stem gasie a 
alike on the fertile and sterile plants, but the branches have anon 
method of arrangement. On the leaf of the branch (Fig. 
there is no central furrow, but its place is taken by 4 tat rA 
(Fig. 6 m),and the ridges and furrows of the leaf are 4t SY 
either side of the ridge (4 4), but on the stem they pass don 
the furrows and lie on either side of the lowest part. 5 tote i 
This arrangement of stomata in Æ. arvense 15, the $ : 
species, for in Æ 4imosum and E. hyemale they lie, on "3 
exclusively in the furrows. 
EXPLANATION OF PLATE XXXII. 
FIG, 1.—Epidermis of stem (preserved in alcohol). 
Fic. 2.—Cross-section of a stoma. 
Fic. 3.—A mature stoma. 
Fic. 4.—Cross-section of leaf of fertile plant. 
Fic, 5.—Cross-section of ridge of stem. 
Fic, 6,—Cross-section of leaf of branch. 
—Lffie A. Southworth, Ann Arion, Ms 
Tae Desmips or THE Unirep States.—A om i 
be given to the study of these beautiful plants by r nited S 
of Rev. Francis Wolle’s book, Desmids of the ©” and" 
lately received. Over four hundred and fifty species 
