simple to lobed or decompound; flowers naked, solitary, perfect, arising from a 

 spathelike involucre; perianth wanting or composed of 3 to 5 scalelike or mem- 

 branous sepals; stamens 1 to many; fruit a 2- or 3-celled many-seeded ribbed 

 capsule. 



About 130 species in more than 40 genera, mostly tropical. 



1. Podostemon Michx. River-weed 

 Characters of the family. More than a dozen species of wide distribution. 



1. Podosfemon Ceratophyllum Michx. Thread-foot. Fig. 480. 



Plant olive-green, firm, glabrous; leaves long-petiolate, rigid, divided into linear 

 or filamentous segments or sometimes simple, with dilated base sheathing the 

 stem; stems abbreviated to very elongate, sometimes as much as 6 dm. long or 

 more; flowers green, arising along the stems or in clusters at apex of stems, with 

 slender pedicels; perianth obsolete; stamens 2, the more or less united filaments 

 exceeding the ovary; ovary 2-celled; stigmas 2, subulate; capsule unequally 

 2-valved, with one 5-ribbed valve persistent, broadly ellipsoid, 2-3 mm. long. 



Attached to rocks in streams and rivers in Okla. (McCurtain Co.) and (?) e. 

 Tex., May-July; from Ga., along the Gulf Coast to Okla., n. to Ont. and N. B. 



Fam. 69. Crassulaceae DC. Orpine Family 



Annual or perennial succulent exstipular herbs with perfect symmetrical flowers 

 usually in a cyme; leaves alternate or opposite, simple or sometimes dentate; 

 petals (free or somewhat united) and pistils the same number as the calyx seg- 

 ments and the stamens the same or double their number; fruit a 1 -celled follicle 

 that opens down the ventral suture, 1- to many-seeded. 



About 1,500 species in 35 genera that are world-wide in distribution. 



1. Plants minute, spreading or decumbent; leaves opposite and connate at base, 

 7 mm. long or less; flowers solitary or in glomerules usually in axil 

 of leaves; stamens as many as calyx segments; follicles 1.5-2 mm. 

 long 1. Tillaea 



1. Plants ascending or trailing; leaves not opposite, usually more than 10 mm. 

 long; flowers in spreading cymes; stamens twice as many as the 

 calyx segments; follicles 4-6 mm. long 2. Sedum 



1. Tillaea L. Pigmy-weed 



About 20 species of world-wide distribution. 



1. Tillaea aquatica L. Water pigmy-weed. Fig. 481. 



Tufted or matted diminutive more or less aquatic annual, glabrous throughout; 

 stems filiform, much-branched from base, spreading or decumbent, to 10 cm. 

 long; leaves opposite, connate-perfoliate, linear to linear-oblong, entire, to 7 mm. 

 long; flowers minute, solitary, axillary, 4-merous, essentially sessile or with 

 pedicels longer than the leaves; calyx 1 mm. long, about half as long as the 

 greenish-white petals; follicles ovoid, 1.5-2 mm. long, 8 to 10-seeded. Crassula 

 aquatica (L.) Schoenl., Tillaeaslrum aquaticum (L.) Britt. 



On dry mud flats about pools and along shores, sometimes in water, in e. 

 and s.e. Tex., May-Aug.; from Nfld. w. to Wash., Ut., Wyo. and Tex., s to Md. 

 and La.; also Mex. 



Plants with some of the pedicels exceeding the leaves have been segregated as 

 var. Drummondii (T. & G.) Jeps. [Tillaea Drummondii T. & G., Crassula 

 Drummondii (T. & G.) Fedde, Tillaeastrum Drummondii (T. & G.) Britt.] 



994 



