47 2 FLORA. 



Carpels fewer than the calyx-segments. 



Staminodia present; carpels 3 or 4, wholly united into a one-celled ovary. 



Fam. 4. I'arnassiaceae. 

 Staminodia none; carpels mostly 2, their upper part at least distinct. 



Fam. 5. Saxi/ragaceae. 

 Shrubs or trees. 



Leaves opposite. Fam. 6. Ilydrangeaceae. 



Leaves alternate. 



Fruit a 2-celled, thin-walled capsule; its base adnate to the calyx. 



Fam. 7. Jteaceae. 

 Fruit a i-celled berry. Fam. 8. Grossulariaceae. 



Fruit a 2-celled woody or hard capsule. Fam. 9. Haviamelidaceae. 



f f Endosperm none, or very little (copious in Opulaster, shrub of the Rosa- 

 ceae); leaves mostly with stipules. 

 X Trees with broad leaves and small monoecious densely capitate flowers. 



Fam. 10. Platanaceae. 

 X X Flowers perfect, or if dioecious or monoecious not densely capitate, 

 a. Flowers regular. 

 Pistils usually several or numerous; if one only (as in Cercocarpus and sometimes in 

 species of Alchemilla and Sanguisorba) it becomes a dry 1 -seeded achene. 

 Carpels distinct, rarely adnate to the calyx, ripening into follicles or achenes. 



Fam. 11. Rosaceae. 

 Carpels united, enclosed by the calyx-tube and adnate to it, the fruit a pome. 



Fam. 12. Pomaceae. 

 Pistil only 1. 



Ovary 2-ovuled; fruit a drupe; leaves simple. Fam. 13. Drupaceae. 



Ovary several-ovuled; fruit a legume ; leaves 2-3-pin n ate. 



Petals valvate in the bud. Fam. 14. Mimosaceae. 



(Petals imbricated in the bud: Gleditsia and Gymnocladus in the Caesalpiniaceae.) 

 b. Flowers irregular (nearly or quite regular in Gleditsia and Gymnocladus, 

 trees of the Caesalpiniaceae). 

 Fruit a legume; upper petal enclosed by the lateral ones in the bud; leaves com- 

 pound, mostly stipulate. Fam. 15. Caesalpiniaceae. 

 Fruit spiny, indehiscent; leaves simple, estipulate. Fam. 16. Krameriaceae. 

 Fruit a legume or loment ; upper petal enclosing the lateral ones in the bud; leaves 

 compound (sometimes i-foliolate), stipulate. Fam. 17. Papilionaceae. 



Family 1. PODOSTEMACEAE Lindl. 



River-weed Family 



Small aquatic herbs, the leaves usually poorly differentiated from the 

 stem, the whole structure commonly resembling the thallus of an alga or 

 hepatic, the small usually perfect flowers devoid of any perianth and sub- 

 tended by a spathe-like involucre, or in some genera with a 3-5-cleft 

 membranous calyx. Stamens hypogynous, only 2 in the following genus, 

 numerous in some others; anthers 2-celled, the sacs longitudinally de- 

 hiscent. Ovary 2-3-celled ; ovules, usually numerous in each cavity, anat- 

 ropous ; styles 2 or 3, short. Capsules 2-3-celled, ribbed. Seeds nu- 

 merous, minute, without endosperm ; embryo straight. About 21 genera 

 and 175 species, mostly in the tropics. 



1. PODOSTEMON Michx. 



Flowers sessile or very nearly so in the spathe-like involucre. Perianth none. 

 Stamens 2, their filaments united to near the summit; anthers 2, oblong or oval. 

 Staminodia 2, filiform. Ovary ovoid, 2-celled ; stigmas 2, short, subulate. Cap- 

 sule ovoid. 6-10-ribbed, 2-valved. [Greek, stalked-stamens.] About 12 species 

 of wide geographic distribution. 



1. Podostemon Ceratophyllum Michx. Rivi-.R-WF.En. Thread-foot. 

 (I. F. f. 18 8.) Plant dark green, rather stiff, firmly attached to stones in running 

 water, densely tufted, 2-25 cm. long, the leaves sheathing at the base, commonly 

 split above into almost filiform segments. Flowers less than 2 mm. broad, at length 

 bursting from the spathes ; capsule oblong-oval, rather more than 2 mm. longr. ob- 

 tuse, borne on a stipe of about its own length, 8-ribbed. In shallow streams, Mass. 

 to N. V., Ont, Minn., Ca., Ala. and Ky. July- Sept. 



