732 RICCIACEA. 



thickened at the apex, with delicate whitish obliquely ovate appressed scales , 

 rootlets wanting beneath above the middle ; fruiting plant unknown. Dried 

 up pools and ditches, Canada to Mo., and southward. An analogous form has 

 been developed by Lindberg from R. natans. 



9. R. tenuis, Aust. Thallus thin, olive or yellowish-green, shining, the 

 2-4 divisions roundish-obovate, 2 - 4" long, flat, with sinuate margins, green 

 beneath with a slender costa and few rootlets ; capsule very delicate, closely 

 adherent to the substance of the thallus, minutely apiculate ; spores round or 

 short-oval, conspicuously depressed at one end when dry. Wet ground in 

 open woods, Closter and Lawrence, N. J. (Austin), and Mo. (Hall). 



3. RICClfeLLA. Thallus linear, dichotomous, floating or rarely terrestrial; 

 capsule protuberant from the lower surface. 



10. R. fluitans, L. Thallus often in extended patches, thin, green, ra- 

 diately expanding, the often imbricate divisions ^ - 1-J" wide, parallel-nerved, 

 flat, without rootlets, cavernous only toward the slightly dilated very obtuse 

 or subtruncate apex ; capsules present only in some terrestrial forms, very 

 prominent below, rupturing beneath the apex. Very variable. The most not- 

 able form is var. SULLIV!NTI, Aust., with divisions about -J" wide, channelled, 

 cavernous throughout, the margins crisped-crenulate, and rootlets numerous 

 on the costa tumid with abundant capsules, which are tipped with a long 

 funnel-mouthed point; spores obscurely angled, reticulate and margined. 

 (R. Sullivanti, Aust.) In ponds or ditches or growing in wet places upon 

 the ground ; the variety often in cultivated fields. (Eu.) 



4. RICCIOCARPUS. Thallus obcordate t floating or rarely terrestrial ; cap- 

 sules not protruding, at Length exposed by a cleft in the central groove. 



11. R. natans, L. (PI. 22.) Divisions obcordate or cuneate, broadly 

 emarginate, 3 - 6" long, purplish, very narrowly channelled, with numerous 

 uniform air-cavities beneath the epidermis, rooting toward the base and at 

 length with dark purple scales beneath the apex ; capsules in 1 or 2 rows 

 beneath the groove; spores black, angular, strongly papillose. Canada to 

 the Gulf. (Eu.) 



2. SPH.EROCARPUS, Micheli. (PI. 22.) 



Thallus lobed, without costa or epidermis. Involucres sessile, obconic o* 

 pyriform, perforated at the apex, continuous with the thallus at base. Calyp- 

 tra closely investing the single globose indehiscent capsule, crowned with a 

 deciduous point. Spores globose, muriculate, remaining united in a coccus. 

 Antheridia borne in follicular bodies on the surface of a separate thallus. 

 An anomalous genus, perhaps more closely related to the Jungermanniacese. 

 (Name from a-Qcupos, a sphere, and Kapir6s, fruit.) 



1. S. terr^stris, Smith. Thallus orbicular, 3-6" broad, covered by 

 the clustered inflated involucres, which are nearly 1" long, 3-4 times the 

 length of the capsule ; coccus 102 - 127^ wide, indistinctly lobed. (S. Michelii, 

 Bellardi.) In cultivated fields, mostly southern. (Eu.) 



