82 EQUISETUMS AND CALAMITES. 
and furrows which alternate in succeeding internodes, the fibro-vas- 
cular bundles being always superposed to the ridges, and thus alter- 
bundle forks and unites with that of the next internede, thus forming 
a regular reticulated hollow cylinder in the stem not unlike that in 
the Ferns. A bundle also runs from each of the teeth of the sheath- 
leaf and joins that in the internode. Lach fibro-vascular bundle con- 
tains a lacuna or air canal, which will also be superposed to the 
ridges, while the lacune in the cortical portion of the stem, when 
present, are superposed to the furrows. The points of the sheath- 
leaves correspond to the ert and a fibro-vascular bundle runs up into 
each. The buds and roots produced at the base of the sheath-leaves 
form between the fibro-vascular bundles running to the apices of 
these leaves. 
e cone-like fruit of the Equisetum consists of a 
of modified leaves. At first there is a modified sheth-let, 
the ring, a bract-like structure beneath the cone. come 
whorls of modified leaves, which, by the peculiar growth of the outer 
part, form more or less hexago nal shields supported on a narrow stalk. 
The shield gives rise to ge m 5to 10 sporangia, each developed, 
according to Hofmeister. per ierene a single superficial cell. 
This rapid description of the general characters of Equise will 
suffice for our purpose, and we shall now direet our attention path 
(ad 
° 
> 
© 
2 
=] 
=] 
o 
] 
S 
Be 
«qf 
[=] 
et 
> 
@o 
<4 
) 
ae 
° 
| 
na 
‘ 
Rn 
NATOMY OF Eguisretum. ~ Whe en viewed with a low. 
power the stem exhibits a more or less large central lacuna or air 
space. Surrounding this are the separate fibro-vascular bundles, 
arranged in a circle,.and separated from the fistular central cavity 
by a few cells, mostly pesensbryineons, the remains of the pith. Each 
fibro-vascular bun dle is supplied with a lacuna elvireny its inner bee, 
neral chiefly parenchymatous, with lac cune; but in many cases 
Pande of — thick-walled cells oce ur. 
tial ace 
