INTRODUCTION. 
lately cylindrical. In J. pubescens (tab. 73) and J. fur cat a, (tab. 55) they appear to be 
so; but, in J. Blasia, J. pinguis, and J. multifida, they are much depressed. They are 
prostrate or procumbent in J. Lyellii (tab. 77), J. hibernica (tab. 78), and most of this 
family . erect in J. multifida (tab. 45) ; in which species likewise occur examples of vague 
and regularly pinnatifid ramification. In J. furcata (tab. 55) the branches are dichotomous. 
In the same plant, too, and in J . Jjyellii (tab. 77) and J. epiphylla (tab. 47), innovations 
are very common. 
The principal difference between the Jungermannia, frondosce and the J mgermannia Jungermannia 
foliosce, consists in the stems of the latter being provided with processes, which, from frondoss and 
their similarity to the leaves in the phaenogamous plants, are distinguished by the same ° 
name, whilst, in the former, the stems are either wholly naked, or are furnished with 
marginal expansions throughout their entire length, which, though of the same nature as 
the leaves, and though lobed, and even pinnatifid, as in J. Blasia (tab. 82), are never so 
deeply cut as to entitle them to that appellation. Among these may be reckoned J. epiphylla, 
J. Lyellii, J. hibernica, J. furcate, and J. pubescens ; and, of the naked-stemmed species, 
J. pinguis and J. multifida are the only ones with which I am acquainted. 
The structure of the stems is very simple, and altogether cellular. The cellules structure of 
small, separated by thin pellucid membranes ; their figure oblong ; and their substance the Stems ' 
filled with a colorless fluid, mixed with extremely minute granules, of a green olive or 
purple color, when the plant is in vigor, which consequently gives the same tinge to the 
whole of the stems. When these are of a dirty brown color, it arises, probably, from an 
injured and decayed state of the outer cellules ; and the stem then becomes brittle : it is 
otherwise pliable, and, in the younger plants, even flaccid. 
LEAVES. 
The leaves of Jungermanniae vary remarkably in their insertion, direction, and figure, Leave*, 
and generally afford excellent specific marks of discrimination among the species. 
No instance whatever is known of the leaves of these plants being situated on foot- insertion ami 
stalks : they are always sessile, and not even contracted at the base ; but, in many instances, base ‘ 
as, for example, in J. asplenioides (tab. 13) and J. spinulosa (tab. 14), they are decurrent. 
In almost all the species with bifarious leaves, they have an oblique insertion ; that is to 
say, one angle of the base rs fixed in the back of the plant, whilst the opposite one is seen 
before it: thus the leaf is obliquely semiamplexicaul. In the species with multifarious 
leaves, such as J. Hookeii, J. setiformis (tab. 20), &c., the base half embraces the stem 
transversely. In J. pusilla (tab. 69) the leaves have their base running parallel with the 
stem. 
In all the plants with bifarious leaves, either the superior or the inferior surface of the Imbrication, 
stem is more or less concealed by the imbrication of the leaves; and these two kinds 
of imbrication afford excellent characters for subdividing the genus. Thus, in J. hyalina 
(tab. 63) and J. Sphagni (tab. 33) the imbrication is inferior; whilst in J. Mackaii (tab. 53), 
J. HutchinsicE (tab. 1), J. Trichomanis (tab. 79), and J. dilatata (tab. 5), it is superior 
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