124 PROCEEDINGS OF THE AMERICAN ACADEMY 



IX. 



CONTRIBUTIONS TO AMERICAN BOTANY. 

 By Sereno Watson. 



Presented June 12, 1889. 



1. Miscellaneous Notes upon North American Plants^ chiefly 

 of the United States, ivith Descriptions of New Species. 



Akabis iiumifusa {Sisymhrium liumifusum, Vahl). The typical 

 form of this Greenland species has been collected at Ungava Bay in 

 northern Labrador by Mr. L. M. Turner, and a form with the lower 

 leaves and base of the stem pubescent at York Factory on Hudson's 

 Bay by Mr. James M. Macouu and Dr. Robert Bell. The mature 

 pods of this variety are those of an Arahis, with the seeds narrow and 

 wingless, and the radicle partially incumbent upon the cotyledons, as 

 it IS represented in the figure of the species given m Flora Danica 

 (t. 2297). The characters accord with those of several other species 

 which have usually been recognized as belonging to Arabis, though 

 discrepant from the more typical species of the genus. Of these spe- 

 cies (^A. lyrata, A. dentata, A. spathulata, A. humifusa, and A. Hookeri, 

 Lange) I would form a section Pseicdarabis, as proposed by me in the 

 recent new edition of Gi'ay's Manual (p. 67), characterized by very 

 small oblong or elliptical wingless seeds, having the cotyledons rarely 

 strictly accumbent. They are all biennial or perennial, the pubes- 

 cence of simple or rarely forked hairs. 



Arabis Howellii. Perennial, with short stems (1 to 4 inches 

 high) from a branching cespitose caudex, glabrous : leaves glaucous, 

 entire, the lower linear-oblanceolate, an inch long, often sparsely 

 ciliate toward the base, the few cauline narrowly oblong, obtusish, 

 sessile, somewhat clasping but not cordate nor auriculate at base : 

 flowers few, pale or bright pink, 3 or 4 lines long: pods erect, 1^ 

 inches long by 2 lines broad, acuminate; stigma sessile; valves nearly 

 nerveless : seeds orbicular, broadly winged. — Collected at Ashland 

 Butte, Siskiyou Mountains, Oregon, by Mr. Thomas Howell in July, 



