502 E1CCIACEAE. 



Family 1. RICCIACEAE Duinort.* 

 Riccia Family. 



Gametophyte terricolous or aquatic, annual or perennial, once to sev- 

 eral times diehotomous, often forming rosettes, half -rosettes, or flabelliform 

 expansions. Stomata wanting or rudimentary in Riccia, well developed 

 in Oxymitra, moderately well developed in Ricciocarpus. Ventral scales 

 usually obvious. Antheridia and archegonia arising singly from the dorsal 

 surface just back of the growing apex, soon becoming deeply immersed in 

 the thallus. 



Sporophyte a capsule, without foot or seta, enclosed by the calyptra, in 

 which the spores come to lie at maturity through the disappearance of the 

 capsule wall. Inner cells all producing spores or (Oxymitra) an incon- 

 spicuous few of them remaining sterile; spores separating at or before ma- 

 turity, the separate spores large, subspheric or more commonly more or 

 less tetraheclral, with a rounded outer face and plane inner faces, the sur- 

 faces marked with free or most frequently mesh-forming ridges, or simply 

 with spines, the angles of the areolae often with papilliform elevations, the 

 inner (plane) faces usually less strongly marked than the outer. 



1. RICCIA [Micheli] L. Sp. PL 1138. 1753. 



[Eicciella A. Br. Flora 4: 756. 1821.] 



Gametophyte terricolous or rarely aquatic, usually several times dicho- 

 tomously branched. Assimilatory layer consisting of vertical or subvertical 

 columns of cells bounding very narrow air-canals, or consisting of larger poly- 

 hedral or subclavate chambers bounded by unistratose lamellae. Stomata 

 represented by very inconspicuous pores bounded by unmodified or only very 

 slightly modified epidermal cells. Latero-ventral scales hyaline-albescent, 

 brownish, violet, or dark purple, rarely surpassing the margins of the thallus, 

 sometimes apparently wanting. Antheridia and archegonia scattered, the an- 

 theridia irregularly intermingled with the archegonia in the monoecious species, 

 with occasional tendencies to segregation, both destitute of a special involucre. 

 Sporophyte-wall unistratose throughout, soon disintegrated. Spores separating 

 at or before maturity. Accessory sterile cells wanting. [Commemorates P. F. 

 Eicci, a Florentine senator and patron of science.] A genus of 130 or more 

 species, of temperate and tropical distribution. Type species: Riccia crystal- 

 Una L. 



Thallus margins and sides green or occasionally tinged with red-purple ; dorsal sur- 

 face vesicular-areolate, becoming spongiose or lacunose-alveolate ; spores distinctly 

 angled and wing-margined. 1. R. crystallina. 



Thallus margins and sides dark violet or blackish : dorsal sur- 

 face rather obscurely and finely reticulate, remaining firm and 

 intact ; spores obscurely angled, destitute of wing margins. 2. R. violacea. 



1. Riccia crystallina L. Sp. PI. 1138. 1753. 



Thalli small to moderately large, 2-6 times diehotomous, forming rosettes 

 5-20 mm. (rarely 30 mm.) in diameter, or soon irregularly gregarious, usually 

 a light crystalline green, occasionally dark green or now and then tinged with 



* Contributed by Dr. Marshall A. Howe. 



