VOL. IV.] Colorado Plants. 5 



the coat, which is less deeply pitted; the seeds are larger. The 

 pods of A. hispidct are ovate, and when they dehisce the seg- 

 ments are acuminate. In A. platyceras the pods are veiny and 

 the segments acute. I have seen no intermediate forms which 

 might connect these two that seem so diflferent. 

 .^ Erysimum asperum DC. This widely distributed species, as 

 found on the plains, is low and stout, with pods often four inches 

 long, numerous and perpendicular to the stem. The pods are 

 stiff, and, projecting as they do, remind one of the spears of a 

 Macedonian phalanx. The flowers are 3'ellow. The variety at 

 Silverton, in the San Juan Mountains, has the color of the flowers 

 from pale yellow, almost white, to orange on the one hand, and 

 through shades of pink and crimson to purple on the other. 

 These different shades were found in one patch and seemed to 

 indicate that the common yellow form had become mixed with a 

 purple variety. The mountain form is more slender than the 

 prairie plant, and the pods are ascending. 



Arabis HolbcELLIi Hornem. This is one of the most 

 puzzling of the western Cruciferas because of its great variety of 

 forms. If there are any plants of A. Holbcellii with, one row of 

 seeds in each cell, wherein does it differ from A. ca7iesce?is, which 

 also has stellate pubescence and deflexed pods ? The division, if 

 A. canescens is a good species, should be thus: Pods deflexed 

 or spreading, seeds in one row, A. canescens; seeds in two rows, 

 A. Holboellii. If pods containing both one and two rows of seeds 

 are found on the same plant of A. Holbcellii, then A. cayiescens 

 ought to be included under A. Holbcellii. Including under A. 

 Holboellii all the forms that are perennial and have pods deflexed 

 or spreading, with two rows of seeds in each cell and pubescence 

 generally stellate, the following forms should be described in 

 order to make the species better understood: 



I. From Mancos, Colo. Stem simple, stout, tall, thickly 

 clothed at base with white branching hairs, but not stellate, 

 above glabrous and glaucous; radical leaves from spatulate to 

 oblanceolate, sparingly dentate or entire; cauline leaves sagittate- 

 clasping, pedicels spreading upwards and outwards, pods deflexed 

 or horizontal, glabrous; winged seeds, two rows in each cell, 

 petals twice as long as the stamens, erect. 



\y 



