T2 Cavers: Notes on YVorkshtre Bryophytes. 
leaves. Here and there the plant is attached to the substratum 
by a tuft of rhizoids (‘root-hairs’) springing from the base of an 
underleaf. The leaves are spirally arranged, so that one under- 
leaf corresponds to two sideleaves. Each sideleaf is attached 
to the stem by a narrow insertion, which is exactly transverse 
in the young leaf, but later becomes shifted so as to run slightly 
forwards above (the line of insertion changes from | to\, looking 
at the stem from the side, with the growing forward end on the 
left), and the leaf curves so that its fore edge covers the hinder 
edge of the next leaf in front (the ‘incubous’ arrangement). The 
underleaves, however, keep their original transverse insertion. 
Each leaf is divided into two lobes. In the underleaves, 
this division is not very deep; the middle of the free part of the 
leaf is more or less deeply notched, the two teeth being of about 
the same size and*shape. In the sideleaves, the two lobes are 
sharply separated to the base; the relative size of the lobes 
varies in different species and individual plants, even on the 
same plant, but the upper lobe is always the larger. While 
the upper lobe is a flat or curved plate, the lower lobe has the 
form of a pitcher which serves for storing water. This pitcher 
(‘lobule’ or ‘ auricle’) is open behind and is joined to the upper 
lobe by a narrow stalk inserted near the mouth of the pitcher, 
and on this stalk there is usually a short outgrowth (‘stylus’) 
consisting of a single row of cells or a triangular plate (Fig. 1). 
The pitchers, which sometimes contain small organisms (e.g. 
Nostoc and other alge, rotifers, insect-larvee), differ considerably 
in shape in different species, besides varying to some extent in 
the same species or on the same plant. In /. d/atata they are 
usually helmet-shaped, with a wide oblique opening; in the other 
British species they are more cylindrical with a narrow trans- 
verse opening. In many of the tropical species (Fig. 1) the 
pitchers have curious shapes; the mouth is often drawn out like 
a scoop and is sometimes toothed, the closed end may be covered 
with small outgrowths, and in one case (/ replicaza) the pitcher 
is reversed, having the opening facing forwards. 
In order to get a clear idea of the organisation of Frullanza, 
it is necessary to study the early stages of development, by 
means of sections through the tip of the main stem or of a 
branch. The growing point has an apical cell, shaped like a 
pyramid with a slightly curved base, projecting forwards, and 
three flat sides, two of which meet in the middle line above, 
while the third is parallel with the lower surface of the stem 
(Fig. 2). From the three flat sides are cut off three sets of seg- 
Naturalist, 
