MARCHANTTACEAE. 503 



red-purple or brownish red, concolorous' below, the dorsal surface vesicular- 

 areolate, soon becoming spongiose or lacunose-alveolate ; main segments 1-2.5 

 mm. wide; margins obtuse or subacute, naked; scales wanting or rudimentary; 

 transverse sections mostly 2-4 times as broad as high; dorsal epidermis soon 

 indeterminate, the cells of the primary stratum subspheric, ellipsoidal or papilli- 

 form, irregularly collapsing or subpersistent, they or their successors finally 

 40-110/u. in maximum diameter; air-chambers elongate-polyhedral, separated 

 by unistratose lamellae; monoecious (rarely dioecious?); antheridial ostioles 

 elevated 75-250 p; spores at first yellowish brown, soon darkening and often 

 nearly opaque, 60-110 jt in maximum diameter, distinctly angular, with a mar- 

 gin mostly 3-10 /y, wide, the outer face marked with somewhat imperfectly 

 formed areolae usually 10-30 fj, wide or those in the middle sometimes larger 

 ( 30-45 jit) and enclosing a free-ending spur or an isolated tubercle, the inner 

 faces with tubercles, short, free irregular ridges, or sometimes with imperfect 

 areolae, the older spores commonly tuberculate-papillate in profile. 



On wet grounds and in sink-holes, Great Bahama and Exuma Chain : -Vermont 

 to Alberta, Lower California and Trinidad ; Europe. CRYSTALLINE RICCIA. 



2. Riccia violacea M. A. Howe, Ann. Mo. Bot. Gard. 2: 51. 1915. 



Thallus small, 1.5-4 mm. long, simple or 1-3 times dichotomous, irregularly 

 gregarious, rather obscurely and finely reticulate and dark green above, dark 

 violet or blackish at margins and on sides; main segments 0.6-1.15 mm. wide; 

 margins obtuse or rounded, commonly erect-connivent or inflexed on drying, 

 bearing especially toward the apex and often low on the sides* numerous or 

 occasional violet or sometimes hyaline conic or subcylindric acute or obtuse 

 papillae 20-110/* long and 25-45 //, broad at base; scales very short or rudi- 

 mentary, dark violet, rarely overlapping, commonly divided into a series of 

 small irregular often tooth-like laciniae, each consisting of only a few cells; 

 transverse sections 1.5-2 times as broad as high; dioecious (?); antheridial 

 ostioles elevated 20-150 /u, often violet; spores soon fuscous and very opaque, 

 SO 105 /u in maximum diameter, obscurely angled or flattened-sphaeroid, desti- 

 tute of wing margins, finely, irregularly, indistinctly, and almost uniformly 

 areolate over whole surface, the areolae 7-11 M wide, soon very obscure and the 

 spores appearing minutely and densely verruculose. 



On moist ground, Eleuthera : Mona Island ; Porto Rico ; Cuba ; and northern 

 Mexico. VIOLET RICCIA. 



Family 2. MARCHANTIACEAE Corcla. 

 MARCHANTIA FAMILY. 



Thallus (except in Dumortiera) with a distinct dorsal layer of air- 

 chambers, communicating- with the outside air by means of epidermal pores. 

 Ventral scales in two (or more) longitudinal rows. Antheridia and arche- 

 gonia borne on more or less definite receptacles; antheridial receptacles 

 discoid, sessile or stalked; carpocephala discoid, invariably stalked, the 

 stalk sometimes with one or two rhizoid-furrows. Sporophyte differen- 

 tiated into a capsule, stalk and foot, the capsule forced through the calyptra 

 at maturity by the elongating stalk and dehiscing irregularly or by means 

 of a more or less distinct lid; elaters present in the capsule. Gemmae 

 discoid, present in two genera. About 25 genera and 200 species, widely 

 distributed, especially in warm regions. 



1. MARCHANTIA [Marehant f.] L. Sp. PI. 1137. 1753. 



Thallus branching dichotomously. Air-chambers with distinct boundaries, 

 forming a single layer; green cells in short, simple or branched filaments rising 



