the A natomy of the genus Setaginella , Spr. 8 1 
variation occurs in the precise form of the ligule, even in 
the same plant ; but, on the whole, within certain limits, the 
outline is maintained fairly constantly for the species. In 
•S. Vogelii (Fig. 15), 5 . Griffithii , 5 . uncinata , &c., the ligule is 
tongue-like and slightly crenate, without papillae. 
The ligule is sunk in the tissue of the leaf-base by a more 
or less massive glossopodium, bearing an intimate relation to 
the cells of the leaf-base. In .S. haematodes , for example, 
the glossopodium is scarcely at all sunk, whilst in 5 . helvetica 
(Fig. 17), 6*. laevigata , var. Lyallii (Fig. 21), and others, the 
ligule has a deep and well-marked glossopodium fitting into 
a distinct cup in the leaf-base. In all the species which I have 
examined, the glossopodium is enclosed by a distinct sheath 
of cells which are obviously continuous with the epidermal 
cells— on the one side, of the leaf, on the other, of the stem — 
and which are either cubical or elongated in the plane of the 
long axis of the leaf. These cells, when the ligule reaches 
a certain age, become strongly cuticularized and thick- walled. 
The base of the ligule itself, or glossopodium, is composed of 
specially large and clearly-marked cells with little contents. 
Where there are two rows of these, they are not unlike right 
triangular prisms with the long faces towards the sheath. 
The glossopodium as a whole may be looked upon as a blunt 
wedge, thick in the middle and thinning away rather abruptly 
to either margin. The wedge at its thickest part may be two, 
three, four or even more cells thick. Thus in S. Martensii , 
wS". grand is, S. Vogelii, S. Griffithii, &c., there appear generally 
two such basal cells in any given section taken in the median 
longitudinal plane of the leaf ; in .S. Douglasii, S. Karsteniana , 
S. viticidosa , .S. helvetica , &c., three such cells appear, the 
median cell being cubical or brick-shaped; whilst in S. Braunii 
there are four or even more such cells (Fig. 12). The primary 
number does not seem to me to be in all cases maintained, 
secondary divisions occurring as the ligule grows older. For 
instance, in 5 . spinosa the ligule has three initial cell-rows, 
which may, however, by division become four or even more 
(Figs. 1, 2, 4, 6). 
G 
