283 



DIDYMOCARPI. 30. 



Pods didymous, or with sides distorted or corru- 

 gated, or in A. Breweri oblong-ovate and long-beaked 

 and sulcate only below, 3-5 mm. long (about 7 mm. long 

 in A. Breweri), from ovate to broader than long, mostly 

 corrugated transversely, rather coriaceous, not or but lit- 

 tle inflated, evidently stipitate only in A. Brazoensis, cor- 

 date at base, 2-celled. Flowers about sessile in dense 

 (loose in A. reflexus) heads, sometimes elongating to 

 spikes in fruit, niinute or small, rarely 8 mm. long. Calyx 

 long-villous. Leaflets never acute, small, mostly notched, 

 not over 8 pairs. Stipules not connate. Weak, low and 

 slender annuals (possibly perennials in A. diphacus and 

 Angelinus). Tropical plants growing on prairies and 

 plains. 



KEY. 



A. Pods straight, evidently lonErer than calyx, sharp, or triangular 

 at tip, much obcompressed, broadly bis'jlcate ventrally, at least 

 as long as wide or longer, closely reflexed in short and narrow 

 spikes, with the lower edges incurved on the sides and with ven- 

 tral suture sharp and raised, with the tip rather arcuate, 

 strongly cross-ribbed around the margins, deeply sulcate dor- 

 sally, much distorted and with cross-section nearly that of the 

 letter A without the bar, appearing as if minutely stipitate. 

 Peduncles filiform, axillary. Leaflets notched, not over 5 

 pairs. Stems filiform, widely spreading and much branched. 

 Pods 7 mm. long, oblong-ovate. 266 reflexus. 



Pods 3-4 mm. long and widej not oblong-ovate. 267 nigrescens. 



ZA. Pods 7 mm. long and with conical beak nearly as much more, 

 erect in heads, round to reniform in cross section, not corru- 

 gated. Flowers about 7-8 mm. long. Low annuals. 

 Potis long-beaked. 26S Breweri 



3A. Pods about as broad as long or broader, very obtuse and 

 rounded at both ends, apiculate, didymous, or half-oblate-oval. 

 3AB. Pods scarcely longer than the calyx, about 3 mm. long, 

 coarsely and strongly cross-corrugated, sessile, erect in dense 

 heads, about oval, not obcompressed, not inflated. Flowers 

 : 3-8 mm. long, many, white or purple, with the same tendency 



1 to become rudimentary as in A. nigrescens. Weak annuals. 



Pods 3 mm. long, with cross-section a crescent. 269 didymocarpus. 



Pods ;^-2 mm long, with cross-section flatly tripuetrous-cordate. 



270 dispermus. 



