444 POLYGONACE^E. (BUCKWHEAT FAMILY.) 



1. B. cirrhosa, Banks. Glabrous; leaves ovate or heart-shaped, pointed, 

 entire ; petioles dilated at base and partly clasping, but with no distinct sheath 

 or stipules ; flowers greenish, 2 - 5 in a fascicle from the axil of an awl-shaped 

 bract, these crowded in axillary and terminal racemes; pedicel jointed near 

 the base ; fruiting calyx with the wing I' long. S. 111. to S. C. and Fla. 



ORDER 90. PODOSTEMACEJE. (RIVER-WEED FAMILY.) 



Aquatics, growing on stones in running water, some with the aspect of 

 Sea-weeds, or others of Mosses or Liverworts; the minute naked flowers 

 bursting from a spatlie-like involucre as in Liverworts, producing a 2-3- 

 celled many-seeded ribbed capsule; represented in Xorth America by 



1. PODOSTEMON, Michx. RIVER-WEED. 



Flowers solitary, nearly sessile in a tubular sac-like involucre, destitute of 

 floral envelopes. Stamens 2, borne on one side of the stalk of the ovary, with 

 their long filaments united into one for more than half their length, and 2 short 

 sterile filaments, one on each side; anthers 2-celled. Stigmas 2, awl-shaped. 

 Capsule pedicellate, oval, 8-ribbed, 2-celled, 2-valved. Seeds minute, very nu- 

 merous on a thick persistent central placenta, destitute of albumen. Leaves 

 2-rauked. (Name from irovs,foot, and a'Tri/j.uu', stuten ; the two stamens being 

 apparently raised on a stalk by the side of the ovary.) 



1. P. ceratoph^llus, Michx. Leaves rigid or horny, dilated into a 

 sheathing base, above mostly forked into thread-like or linear lobes. Not 

 rare in shallow streams, E. Mass, to Minn., and southward. July -Sept. 

 A small olive-green plant, of firm texture, resembling a Seaweed, tenaciously 

 attached to loose stones by fleshy disks or processes in place of roots. 



ORDER 91. ARISTOLOCHIACE^E. (BIRTHWORT FAMILY.) 



Twininf/ shrubs, or low herbs, with perfect flowers, the conspicuous lurid 

 calyx ralcate in bud and coherent (at least at bate) with the 6-celled ovary, 

 which forms a many-seeded 6-celled capsule or berry in fruit. Stamens G- 

 12, more or less united with the style; anthers adnate, extrorse. Leaves 

 petioled, mostly heart-shaped and entire. Seeds anatropous, with a large 

 fleshy rhaphe, and a minute embryo in fleshy albumen. A small family 

 of bitter-tonic or stimulant, sometimes aromatic plants. 



1. Asarum. Stemless herbs. Stamens 12, with more or less distinct filaments. 



2. Aristolochia. Caulescent herbs or twining shrubs. Stamens 6, the sessile anther.* 



adnate to the stigma. 



1. ASARUM, Tourn. ASARABACCA. WILD GINGER. 



Calyx regular ; the limb 3-cleft or parted. Stamens 12, with more or less 

 distinct filaments, their tips usually continued beyond the anther into a point. 

 Capsule rather fleshy, globular, bursting irregularly or loeulk-idal. Seeds 

 large, thick. Stemless perennial herbs, with aromatic-pungent creeping root- 

 stocks bearing 2 or 3 scales, then one or two kidney-shaped or heart-shaped 

 leaves on long petioles, and a short-peduncled flower close to the ground in the 

 lower axil ; in spring. (An ancient name, of obscure derivation.) . 



