The foliose species have a distinct stem with leaves ; these
stems are either cylindrical, frontally or laterally compressed, and
various in texture, some being almost ligneous, others loosely
cellulose. In position they are either erect, depressed, procumbent,
or pendant; they are either simple or slightly branched, pinnate
or bipinnate ; their ramification either lateral or postical ; a cross-
section of the stem discloses great variety in the size, arrangement.
and texture of the cells, which affords good characters in the
determination of species.
Rootlets.—Some species are almost destitute of these; in
others they are often very abundant, proceeding from tbe postical
side of the stem, from the base of the stipules, or very rarely from
tbe underside of the postical lobe of some species. They are
usually short, simple or rarely forked, unicellular fibres, sparingly
dispersed or closely clothing tbe postical side of the stem.
In one genus only {Biecia) they are papillose within; all the
others are smooth, semi-transparent or pellucid, sometimes dirty
white, claret or purple coloured.
—The insertion, position, and shape of the leaves are
fully described with each species.
The above diagram illustrates the terms used with reference
to their position on the stem.
Erect, making an angle with the stem of about 10 .
Erecto-patent, making an angle with the stem of about 30°.
Patent, making an angle with the stem of about 50°.
Patent-divergent, making an angle with the stem of about 70°.
Divergent or horizontal, making an angle with the stem of
about 90°.
The cells of the leaves vary in shape and size, having walls
clear and well-defined, with angles thickened or not, most frequently
with smaller oeUs at their angles, called trigones.
The following table of sizes of cells, suggested by the late
Dr. Spruce, has been used in the present work:
C o m p a r a t iv e S i z e s o f L e a f -c b l l s o f H e p a t ic ®.
L a r g e .......................................... •10 mm.
Largish or rather large . ■05 mm.
Moderate or medium size •033 mm.
Smallish . . . . ■025 mm.
S m a l l .......................................... ■02 mm.
Very small or rather minute . •017 mm.
Minute . . . . ■014 mm.
Very minute . -0125 to -01 mm.
T ex tu r e o p L e a v es.—In the frondose species the leaves vary
from a thin lamina, consisting of a single layer of cells, to thick
and fleshy, and numerous cells th ick ; in the foliose they are
always composed of a single layer, in one or two cases a slight
thickening at the base has been observed. Unlike many of the
true mosses, they are destitute of a midrib. In one species
{Diplophyllum albicans) there is a pseudo-nerve, consisting of a
line of thickened cells.
S t ip u l e s , or, as they have been called by various authors,
amphigastria, and underleaves, are postical leaves usually very
small and rudimentary; in some genera they are large and
equalling the leaves and generally of the same texture, but often
absent.
I n p lo r e sc b n c e .—The reproductive organs of the Hepaticse
are of two kinds, the male (antheridia) and the female (pistillidia);
their position affords valuable characters in the determination of
species. The leaves enclosing them are called