356 
MUSCINEM. 
The sexual organs of the Marchantieae are borne on monoecious or dicecious recep- 
tacles \ The antheridia, although springing from cells of the epidermis, are, as in Riccia^ 
depressed in the upper side of the thalloid stem, and overarched by the surrounding 
tissue ; they occur in larger or smaller numbers close together upon receptacles, which 
are discoid or shield-shaped sessile or stalked branches that have undergone a peculiar 
transformation. The archegonia are only in the Targioniege inserted at the apex 
of an ordinary shoot; in the other families they are produced on a metamorphosed 
branch, which rises like a stalk and developes in different ways at its summit; it 
bears the archegonia on its outer or lower side. With the variation in the form of the 
part which bears the archegonia is connected an equally varied mode of envelopment 
of the archegonia by involucres. Since it is impossible to describe these structures in 
a short space, we may take Marchantia polymorpha, the species most perfectly endowed 
in this respect, as an example. The explanation of the figures 241-243 will suffice 
to illustrate at least the most essential points. 
The sporogonium of the Marchantieae, usually shortly stalked, contains elaters which 
radiate from the bottom towards the circumference {cf. Fig. 236). It bursts either at 
Fig. 241. — Marchantia polyiiwrpha ; A a horizontal branch t with two ascending branches which bear maie recep- 
tacles hit; Ä vertical section through an incompletely developed male receptacle hic and the part of the thalloid stem 
a from which it springs ; b b leaves ; h root-hairs in a channel of the receptacle ; o o openings of the hollows in which 
the antheridia a are placed : C a nearly ripe antheridium ; st its pedicel ; iv the wall ; D two antherozoids (these last 
X 800). 
the apex with numerous teeth, or is four-lobed, or the upper part becomes detached as 
an operculum. The peculiar gemmae and their cupules have already been described. 
5. The JungermanniesB. In this family occur forms of which the vegetative body 
is a true flat leafless thallus, as Mefzgeria and Aneura, as well as transitional forms whose 
flat thalloid stem forms leaves on the under surface {Diplolcena), or whose stem, as in 
Blasia, elliptical in section in its early stage, becomes broad and leaf-like when older, and 
produces leaves on both surfaces. Closely allied to these is a genus ' with a less dilated 
stem, though still always greatly flattened on the upper side, and bearing leaves only 
above, (Fossombronia ?). The greater number of the genera, however, the foliose Junger* 
mannieae, form a slender filiform stem, with numerous sessile leaves with broad inser- 
tions but distinctly differentiated ; these leaves commonly occurring only in two rows 
situated on the upper side, as in Radula, some species of Jungermannia, Lejeunia, and 
Plagiochila. Typically, however, there are three rows of leaves, one being developed on 
the under or shaded side (hence termed Amphigastria), the other two rows on the upper 
side {Frullania, Madotheca, Mastigobryum). In the flagelliform branches the leaves 
remain very small, and are sometimes almost invisible. 
^ [Leitgeb, Die Inflorescenzen der Marchantiaceen ; Sitzber. d. Wien. Akad. t88o.] 
