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, These 
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, m 
A. Angelinus from the Valley of Mexico.. 
