GROUP II. BRYOPHY/TA: HEPATIC^. 343 



in terminal groups on short ventral branches. A single sporogonium is de- 

 developed in each group of archegoiiia, and becomes enclosed in a perichffitium ; 

 it dehisces by teeth, but in Cyathodium a small operculum is also formed. The 

 pores of the air-chamber layer are simple; a formation of filamentous assimila- 

 tory tissue in the air-chambers occurs in Targionia. 



d. Composites, including Fegatella (Conocephalus), Lunularia, Dumortiera. 

 Preissia (Chomiocarpon), and Marchantia; characterised generally by the com- 

 pound (branched) nature of the gametophore : however, the archegoniophore is 

 unbranched in Fegatella, and in Fegatella and Lunularia there is no antheridio- 

 phore, the male receptacles being sessile on the dorsal surface of the thallus. 

 The air-chambers contain filamentous assiinilatory tissue ; the pores are com- 

 pound in Preissia and Marchantia ; the air-chamber layer is degenerate in 

 Dumortiera. 



Order II. Jungermanniaceae. 



A. The G-AMETOPHYTE. On germination the spore gives rise to a protonema 

 which may be a solid ellipsoidal mass of cells (as in Pellia) with a root-hair at 

 one end ; or a flattened plate of cells (Eadula, Frullania) ; or a filament, some- 

 times branched (Lophocolea, Chiloscyphus); however, the differences in form of 

 the protonema are not of great morphological importance since, in many cases, 

 flattened and filamentous forms have been found to be produced from spores of 

 the same plant. 



The protonema gives rise to the adult shoot by the formation, either from a 

 marginal cell, if it is flat, or from the terminal cell, if it is filamentous, of a 

 growing-point with a single apical cell. 



The Morphology of the Adult Shoot. The adult shoot may be differentiated 

 into stem and leaf, as in the foliose forms ; or undifferentiated, as in the thal- 

 loid forms. Its symmetry is generally dorsiventral ; the only radially sym- 

 metrical, erect-growing forms being Haplomitrium and some species of Eiella 

 (e.g. JR. helicophylla and Parisii). 



The morphology of Eiella demands special notice. It is a foliose form, and 

 is peculiar in that the stem bears, on one side, a membranous wing which is 

 more or less well-developed in the different species. Eiella Notarisii and 

 Reuterl are prostrate dorsiventral forms, and in them the wing is on the dorsal 

 surface of the stem : R. helicophylla and Parisii are radial and erect ; in the 

 latter both the stem and the wing are vertical ; in the former the wing is spir- 

 ally wound round the erect axis. 



Most of the thalloid forms (except Pellia, Aneura, Sphterocarpus) have a 

 distinct midrib. The shoot bears numerous unicellular root-hairs, as also 

 club-shaped glandular hairs which secrete mucilage, on its ventral (under) 

 surface. 



In the dorsiventral foliose forms, the stem bears a row of leaves on each flank, 

 and generally a row of amphigastria on its ventral surface ; amphigastria, are, 

 however, absent or rudimentary in some forms (e.g. Fossombronia, Androcryphia, 

 Petalophyllum, Kadula, Lejeunia calcarea, Jungermannia bicuspidata, Scapania, 

 species of Eiella, etc.), but are represented (except Eadula and Lejeunia cal- 

 carea} by papillae bearing glandular hairs. In Blasia there are two rows of 

 amphigastria as well as ventral scales. The ventral surface of the shoot also 

 generally bears root-hairs, springing from the superficial cells of the stem, but 



