^5^ 



MUSCINEJE. 



The sexual organs of the Marchantieae are borne on monoecious or dioecious recep- 

 tacles ^. The antheridia, although springing from cells of the epidermis, are, as in Ricciay 

 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 Targionieae 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. — Mai-cnantia polymurpha; A a horizontal branch t with two ascending branches which bear male recep- 

 tacles hit; K vertical section through an incompletely developed male receptacle hti 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 ; iu the wall ; D two anthernzoids (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 Jungerm.annie8B. In this family occur forms of which the vegetative body 

 is a true flat leafless thallus, as Metzgeria 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 diflferentiated ; 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 {Fridlania, 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.] 



