HE PA TIC.E. 



3^5 



their fertilised oosphere the globular sporogonium with a wall consisting of a single layer 

 of cells, and entirely filled with spores, without elaters. The spores are set free by the 

 decay of the surrounding tissue. 



4. The Marchantiese have all a thalloid stem extended flat upon the ground • 

 it is ribbon-like, dichotomously branched, possesses a mid-rib, and is always composed of 

 several layers ; the under side produces a number of hairs with conical thickenings 



Fir,. 219. — Ricciii c^-lauca ; yl apical region in vertical longfitudinal section ; ar archegonium ; c oosphere (Xs6o) ; B 

 the unripe sporogonium s^ surrounded by the calyptra, which still bears the neck of the archegonium ar (X300, after 

 Hofineister). 



projecting inwards placed upon a spiral constriction of the internal cavity (Fig. 220 bis), 

 and also two rows of leaf-like lamellae, like the Riccieae. The upper side is covered by 

 a very distinctly differentiated epidermis, penetrated by large stomata of peculiar form. 

 Each of these stands, in jNIarchantia, Lunularia, &c. in the centre of a rhombic plate; 

 these plates are parts of the epidermis which overarch large air-cavities, from the bottom 

 of which the cells containing chlorophyll spring in a conferva-like manner, while the rest 



Fig Qfio—Marchantia polymorfha ; A a horizontal branch t with two ascending branches which bear antheridial 

 receptacles /z?< ; A' vertical section through an incompletely developed antheridial receptacle ini and the part of the 

 thalloid stem a from which it springs ; b b leaves ; h root-hairs in a channel of the antheridial receptacle ; o o opemngs 

 of the hollows in which the antheridia a are placed ; C a nearly ripe antheridium ; st its pedicel ; w the wall ; D two 

 antherozoids <these last, x8oo). 



of the tissue is destitute of chlorophyll and consists of long horizontal cells without 

 interstices {cf. Fig. 65, p. 76). 



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

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

 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 



