644 



HEPATIC^ — LICHENES. 



solitary, opening by four valves, no operculum, spores with elaters. 



3. Anthocerotese : thecse pod-like, 

 2-valved, a central columella with 

 elaters. 4. Kicciese, Orystalworts :. 

 thecse solitary, decaying so as to 

 allow the spores to escape, no oper- 

 culum, no elaters (fig. 447, p. 251). 

 Many of the Hepaticse produce 

 gemmse or buds (fig. 488, p. 275), 

 which are developed on the frond 

 in the form of cup-shaped recep- 

 tacles, and ultimately fall off so as 

 to become distinct plants. Mar- 

 ehantia hemispherica has been re- 

 commended in dropsical cases. 

 There are, according to Lindley, 73 

 genera and about 700 species. 



Examples — Marchantia ; Jungermannia ; Anthoceros ; Eicoia. 



Fig. 889. 



Sub-class II. — Amphi«amjE, Thallogen^, Cellulaees. 



Acotyledons composed entirely of cellular tissue, having no distinct 

 axis, nor leaves, nor stomata, propagated by means of spores, wliich 

 are often enclosed in asci. The sub-class corresponds to Endlicher's 

 division of ThaUophyta, and includes the Amphigamse of De Can- 

 doUe and the Gymnosporse of others. 



Order 221. — Lichenes, the Lichen Family. Plants forming a 

 thallus, which is either foliaceous, crustaceous (fig. 891), or pulveru- 

 lent ; these different forms depending on the mode in which the cells are 

 developed and combined. The reproductive organs appear on the frond 

 in the form of protuberances of various kinds (fig. 892 tp), consisting 

 of an outer layer of thick-waUed roundish cells, more dense than the 

 tissue of the thallus, and of a different colour (fig. 893 cc), and of an 

 internal medullary layer (fig. 893 cm), with paraphyses and sporangia 

 lying perpendicularly to the outer layer cc. The 'fructification gradu- 

 ally projects more from the surface, and either remains covered with 

 the outer layer, or bursts through it. When it remains closed, there 

 is a nucleus in the centre. When the fructification bursts through the 



Figs. 889, 890. Organs of fnictiftcation of Jungermannia Tamaiisoi, to iUustrate tlie- 

 natural order HepaticK. Fig. 889. /, Branches ooverecl with imMcated leaves, arranged 

 in a distichous manner. Two of the branches hearing thecae, supported on stalks which 

 arise from an iuTolucre at the base. H, Involucres, c, Thecae closed in the young state: 

 c', Thecae opening by four valves to discharge the spores and elaters. Fig. 890. r, Recep- 

 tacle bearing elaters, e, or spiral filaments, one of which shows the double spiral fibre. 

 5. Free spores. 



