HEPATIC^E. 



[ 387 ] 



HEPATIC^E. 



while they are scattered indiscriminately 

 over the lower face of Marchantia ; and from 

 this line also arise the little bodies resem- 

 bling minute leaves, called amphigastria. If 

 we suppose the frond of Riccia elongated 

 and the mid-nerve more strongly marked, 

 we have the likeness of Bhjttia Lyelli (fig. 

 62, p. 106) ; while if this latter were notched 

 down to the rib at intervals along each side, 

 we should have the stem with two parallel 

 rows of leaves, as in the Jungennannieae. 



Fig. 319. 



Lunularia vulgaris. 

 A frond in fruit. Nat. size. 



The line of insertion of the leaves is 

 seldom exactly parallel with the axis of the 

 plant, and very rarely at right angles. In 

 most cases it is more or less oblique, and 

 the obliquity is in reverse direction at the 

 two sides of the stem, so that the lines of 

 insertion of two succeeding leaves would 

 meet, if prolonged across the stem, in the 

 form of a V (fig. 320). 



The leaves are very frequently imbricated, 

 and they overlap in two ways : either each 

 leaf covers with its lower edge a little of the 

 leaf below it, or each leaf overlaps a little 

 of the base of the leaf above it. In the first 

 case, the leaves are called succubous (fig. 

 320), in the second incubous (fig. 321). The 

 leaves vary much in form, and are often 

 deeply toothed or bilobed, and form exceed- 

 ingly elegant objects under the microscope. 

 The leaves are accompanied in many cases, 

 chiefly in the Jungermannieae, by stipule- 

 like leaflets, called ampliiyastrid) situated at 

 the underside of the stem. 



These plants are reproduced by dust-like 

 grains called spores, by minute cellular no- 

 dules called gemmce, and by innovations, i. e. 

 new lobes growing out from the margins of 

 the old fronds, or buds in the axils of leaves, 



or on confervoid branches set out from the 

 stem. 



The gemmceof Marchantia polymorpha are 

 produced in elegant membranous cups, with 

 a toothed margin, growing on the upper 

 surface of the frond, especially in very damp 

 and imperfectly lighted situations ; they are 

 little cellular nodules at first attached by a 

 stalk, and at a certain period fall off and 

 grow up into a new frond. (See MABCHAN- 

 TIA.) 



Fig. 320. 



Fig. 321. 



Fig. 320. Eadula complanata. Magn. 5 diama. 

 Fig. 321. Plagiochila undulata. Magn. 5 diams. 



The spores are produced in sporanges or 

 capsules, the formation of which is preceded 

 by special anatomical and physiological 

 phenomena demonstrating the existence of 

 distinct sexes in these plants. The organs 

 which represent the anthers of flowering 

 plants are called antheridia; those which 

 represent the ovules, and produce the spore- 

 cases, are called archegonia or pistillidia. 

 The antheridia are small globular or oval 

 bodies, more or less stalked, which in the 

 Jungermannieae are composed of a double 

 layer of cells forming a membranous sac, 

 which, when ripe, bursts and discharges 

 numerous minute globular cellules, each of 

 which again bursts and discharges an ex- 

 tremely small filament, which moves about 

 actively in water (figs. 322 & 324). These 

 organs mostly occur in the same situations 

 as the archegonia ; and in some of the fron- 

 dose forms, such as Anthoceros, Riccia, 

 Fimbriana (fig. 318), &c., they are im- 

 bedded in the substance of the frond; in 

 others, as in Marchantia, they are immersed 

 in the upper part of special male stalked 

 2 c 2 



