PENTHORACEAE. 141 



FAMILY 1. PODOSTEMACEAE. RIVER- WEED FAMILY. 



Aquatic herbs, adhering to the rocks, the vegetative organs resembling 

 the thallus of an alga or a hepatic. Leaves alternate: blades lobed or 

 decompound. Flowers perfect, arising from a spathe. Perianth wanting, 

 or of 3-5 scale-like or membranous sepals. Androecium of 1-many 

 stamens. Gynoecium of 2 or 3 united carpels. Fruit capsular. 



1. PODOSTEMON Michx. Caulescent alga-like herbs. Leaf -blades divided 

 or dissected. Perianth obsolete. Stamens 2. Ovary 2-celled. Capsules un- 

 equally 2-valved, one valve persistent. 



1. P. Ceratophyllum Michx. Stems less than 2 dm. long, usually few cm. long: 

 leaves short and narrow: capsules 2.5-3 mm. long. Susquehanna valley. 

 Occasional, on rocks about islands. Schists. Sum. RIVER- WEED. 



FAMILY 2. SEDACEAE. ORPINE FAMILY. 



Herbs, usually succulent, or partially woody plants. Leaves alternate, 

 opposite, or whorled: blades thick, flat to terete. Flowers perfect or 

 dioecious, cymose. Calyx of usually 4-6 persistent sepals. Corolla of as 

 many petals as sepals, or wanting. Androecium of as many stamens as 

 sepals or twice as many. Gynoecium of as many distinct or partially 

 united carpels as there are sepals. Fruit follicular. 



1. SEDUM [Tourn.] L. Annual or perennial herbs. Leaves alternate, 

 or sometimes opposite or whorled: blades terete, angled, or flat. Flowers per- 

 fect, borne in often 1-sided cymes. Sepals 4 or 5, usually much longer than 

 wide. Follicles spreading. STONECRQP. 



Flowers borne in a terminal corymbose cyme. 1. 8. triphyllum. 

 Flowers borne in simple or branched scorpioid cymes. 



Corolla white : leaves flat, not imbricate. 2. 8. ternatum. 



Corolla yellow : leaves very thick, imbricate. 3. 8. acre. 



1. S. triphyllum (Haw.) S. F. Gray. Plants tufted, 3-5 dm. tall: leaf -blades 

 obovate to oblong or ovate, 2-5 cm. long, coarsely toothed: cyme densely flow- 

 ered, 2-5 cm. wide: sepals lanceolate to ovate-lanceolate, 1-2 mm. long: petals 

 purple or reddish, oblong to ovate-oblong, 4-5 mm. long, acute: follicles 4-5 

 mm. long. N. M. Occasional, on roadsides and about gardens. Nat. of Eu. 



Sum. LlVE-FOR-EVER. 



2. S. ternatum Michx. Plants matted : leaves, at least the lower ones, in 3 ? s, 

 distant, except in the terminal rosettes: sepals linear, 3-4 mm. long: petals 

 oblong-lanceolate to lanceolate, 6-8 mm. long: follicles spreading, 5.5-8 mm. 

 long, long-beaked. Common, in damp places, often on rocks. Spr. 



3. S. acre L. Plants in depressed mats, yellowish-green: leaf -blades very 

 thick, ovate, 2-5 mm. long, imbricate: sepals lanceolate to ovate-lanceolate, 

 2-2.5 mm. long: petals yellow, lanceolate, 5-6 mm. long: follicles spreading, 

 3-4 mm. long, short-beaked. N. M. Occasional, on rocks or in stony soil. 

 Nat. of Eu. Sum. MOSSY-STONECROP. 



FAMILY 3. PENTHORACEAE. VIRGINIA-STONECROP FAMILY. 



Caulescent plants. Leaves alternate: blades toothed. Flowers per- 

 fect, borne in terminal cymes. Calyx of 5 or 6 sepals. Corolla of 5 or 6, 

 inconspicuous veinless petals, or wanting. Androecium of twice as many 

 stamens as sepals. Gynoecium of 5 or 6 carpels united to the abruptly 



