26 



nate stipuled, and hoary A. .hypoleucus with hairs fixed by the 

 middle, from central Mexico. Forms with broad pods and flowers 

 in spikes have two groups those with short spikes embracing A. 

 oxyrhynchus and Seatoni from San Luis Potosi to Oaxaca. Plants 

 with broad pods and long spikes are the the pubescent A. Goldmani 

 from Chihuahua and Clevelandi from western California. Plants 

 with stipitate pods in dense heads are A. Purpusi. 



31. Didymocarpi. This is the natural culmination of the Mic- 

 ranthi. The species are annuals unless A. diphacus and Angelinus 

 are more enduring. The pods are for the most part very small 

 and much altered. The annuals separate into those with pods sessile 

 and those with stipitate pods. The first group contains those with 

 closely reflexed pods in spikes and the species are two, A. reflexus 

 of the Texan prairies, and A. nigrescens of the hot Californian plains. 

 This group also contains with erect pods, A. Breweri with a long 

 beak and relatively large pods, and didymocarpus and dispermus with 

 pods hardly longer than calyx and didymous and corrugated. Those 

 belong to the Californian plains and run over into the border of 

 Arizona and Nevada. The species with stipitate and reflexed pods 

 is A. Brazoensis of the Texan plains and prairies. The apparently 

 perennial species are both Mexican, A. diphacus from Zacatecas, and 

 A. Angelinus from the Valley of Mexico.. 



