34 MARCHANTIACEAE 
Family П. MARCHANTIACEAE. 
Chlorophyll-bearing layer of the thallus (exc. in Dumortiera) 
with well-developed air-chambers, these in most cases containing a 
loose somewhat filamentous assimilative tissue or soon divided into 
smaller secondary chambers by chlorophyll-containing lamellae. 
Stomata (exc. in Dumortiera) always present, simple (2. e., the pore 
surrounded by four or more somewhat modified epidermal cells, 
all in a single stratum) or dolioform (2. e., the pore surrounded by 
a barrel-shaped wall, several cells in height, which projects into 
the underlying air-chamber). Sexual organs nearly always ag- 
gregated, often borne on long-stalked, capituliform receptacles. 
Capsule short-stalked, breaking through the calyptra at ma- 
turity, dehiscing irregularly or by a special lid, rarely valvate. 
Spores always accompanied by sterile cells, which (exc. in thes 
Corsinioideae*) are developed as elaters. 
Key to the Genera of the Marchantiaceae. 
Sporogonium single, underneath the apical margin of the thallus, enclosed by an invo- 
lucre consisting of two rigid, brown or dark purple valves which, previous to the ma- 
' turity of the capsules, are united in a vertical keel-like suture, 2. Türgtonía. 
Sporogonia in groups on stalked receptacles. 
Stomata dolioform ; antheridia on a disk-shaped receptacle ; Ф receptacles (in 
our species) with 8—r1 finger-like, usually decurved rays; gemmae in dorsal, 
cup-shaped, dentate-margined receptacles, то. Marchantia. 
Stomata of the thallus simple 
the gemmae in dorsal, crescentic, entire-margined recep- 
tacles. Found in or about greenhouses. 9. Lunularia. 
25 cm. X .75-1.5 cm.) areolae very distinct, the ele- 
vated stomata easily visible without magnification. The up t 
cells of the thin, sharp!y defined, chlorophyll- earing layer each with a 
ak. 8 
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а membranous, white or sometimes 
violet pseudoperianth, this at first somewhat conical, usually much 
exserted, finally more or less completely divided longitudinally 
into 3-18 narrow segments, LA 
Pseudoperianths wanting or very rudimentary. 
9 branch arisi f Ж, EY | 1 г. 
га tq. 
g face of thallus, eduncle 
without a root-hair furrow; stomata normally stellate (2. г., the 
cells bounding the pore have the radial walls strongly thick- 
ened). 3. Clevea. 
* This subfamily is not represented in North America, so far as is now known. | 
