CRYPTOGAMS 



429 



formed by the overarching growth of the adjoining tissue. This enveloping wall 

 is afterwards ruptured by the elongating capsule, and forms a sheath at its base. 

 The sporogonium consists of a swollen foot and a long, pod-shaped capsule ; it has 

 no stalk. The superficial cells of the foot grow out into 

 rhizoid-like papilla-. The capsule splits longitudinally 

 into two valves, and has a central hair-like columella 

 formed of a few rows of sterile cells (Fig. 383). The 

 columella does not extend to the apex of the capsule, 

 but is surmounted by a narrow layer of sporogenous cells. 

 Elaters also occur ; they are multicellular, variously 

 shaped, and often forked. The sporogonia, unlike those 

 of all other Hepaticae, do not ripen simultaneously 

 throughout their whole length, but from the tips down- 

 wards, and continue to elongate by basal growth after 

 ('merging from the archegonia. The wall of the sporo- 

 gonium possesses stomata, which do not occur in other 

 Liverworts ; chlorophyll is present in its cells. 



On the under side of the thallus, slit-like openings, formed by the separation 

 of the cells, lead into cavities filled with mucilage. Nostoc filaments penetrate 

 into these cavities, and develop into endophytic colonies. 



FIG. 383. Anthoceros Jam's. 

 sp, SiK)rogonium_; c, colu- 



ini'lla. (Nat. sixi>.) 



Order 4. Jungermanniaeeae 



These are usually small forms which grow on the ground or on tree-trunks and 

 in the tropics on the surface of living leaves. In the simplest forms of this order 

 the thallus is broadly lobed, similar to that of Marchantia (e.g. Pellia epiphylla, 

 frequently found on damp ground) ; 

 or, like that of liiccia Jiuitans, it is 

 narrow and ribbon-shaped, and at the 

 same time profusely branched (e.g. 

 .}/</ -.i/cr-ia furcata, Fig. 163). In the 



Ki. 3S4. 



lutia iHisiliii. .-.-, Sporogoninm ; 

 r, rhizoids. (x 2.) 



Fia. 385. Plagiocliila asphniiiules. 

 gonium. (Nat. size.) 



other forms, again, the broad, deeply - lobed thallus has an evident midrib, 

 and its margins, as in the case of Blasia pusilla (Fig. 384), exhibit an in- 

 cipient segmentation into leaf-like members. The majority of Jungerman- 



