щети ниви ит рима EE ке Вела ЫН 
MARCHANTIALES 18 
canals or enlarged air-chambers in the subjacent chlorophyll-bear- 
ing layer. and. are often bounded by specialized epidermal cells. 
Ventral surface mostly provided with scales arranged in longitud- 
inal rows. Root-hairs of two forms upon the same plant, the one 
with smooth walls, the other with interior peg-like papillae. Sex- · 
ual organs aggregated in specialized parts of the thallus or on 
modified branches, or in the lower forms irregularly scattered. 
° The first four segments of the embryo sporogonium arranged 
like the quadrants of a sphere. Matured sporogonium consisting 
of a capsule without stalk or foot, all of the interior cells forming 
spores, or of capsule, foot, and short seta (rarely attaining length 
of 1-2 mm.), when some of the interior cells produce elaters. 
The order Marchantiales comprises the two families Ricciaceae 
(see below) and MJarchantiaceae (see page 34.) 
Family I. RICCIACEAE. 
Gametophyte a carnose, dichotomously branched or rarely sub- 
simple thallus; chlorophyll-bearing tissues of suberect lamellae 
enclosing very narrow and inconspicuous subvertical air-canals or 
more ample chambers, these unoccupied by a specialized assimi- 
lative tissue. Stomata rudimentary, rarely well-developed. Уеп- 
-tral scales mostly present but sometimes obscure. Sexual organs 
arising singly from the dorsal surface just back of the growing 
apex, soon becoming deeply immersed in the thallus, the elongated 
archegonium-neck commonly exserted, the walls of the efferent 
canal of the antheridial cavity often produced into a conico-cylin- 
drical elevation. | 
Sporophyte a capsule, without foot or seta, always enclosed by 
the calyptra, in which the spores come to lie at maturity through 
the disappearance of the delicate capsule-wall. Inner cells all 
producing spores. 
ГАР 1753. Ех Mich. Nov. Р. Gen. 
106. 1729. 
Plants terrestrial, or rarely aquatic, often forming rosettes or 
half-rosettes, with linear, ovate, or cordate lobes, usually closely 
attached to the soil by root-hairs, the latter either smooth-walled 
or furnished with peg-like protuberances from the wall into the 
