VOL. XIX PP. 127-132 SEPTEMBER 6, 1906 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



REVISION OF THE GENUS WISLIZENIA. 

 BY EDWARD L. GREENE. 



Having had occasion to examine minutely the reticulation of 

 the silicles in certain genera of the Cruciferae, I passed to the 

 comparison of these with those of two anomalous members of 

 the family of Capparidaceae, namely Oxi/stylis and Wislizenia, 

 the former a rare, the latter a not very common type, both 

 indigenous to the desert regions of the remote Southwest. 



One of the generic characters of Widizenia, according to 

 authors, is the reticulate and tuberculate superficies of the nut 

 let-like one-seeded twin valves of the fruit. 



In the process of examining the valves, as they appear in a 

 long series of specimens in the National Museum and in my 

 own herbarium, I found those of the original Wislizenia refracta 

 to be in truth, and very beautifully, reticulate as well as slightly 

 tuberculate, this description of valve, or rather nutlet, occurring 

 however in no specimens except such as had come from western 

 Texas and adjacent New Mexico, the peculiar climatic region 

 whence this type species had been derived. These specimens, 

 assorted and separated from the others, left a much more con 

 siderable bundle of mounted sheets that were a medley of things 

 not in any way reconcilable with the species W. refracta, the 

 name of which was on almost all the labels. 



Out of this medley I gathered first a series of sheets, all from 

 a very different climatic region in northern Arizona, in every 

 specimen of which the valves are devoid of any kind of either 

 reticulation or tuberculation and almost smooth ; this plant in 

 habit and aspect also very unlike the real W. refracta. A third 

 series of sheets differing clearly from both the aforementioned as 

 to foliage as well as fruit seemed as clearly to illustrate a species 

 confined, as it would seem, to the low and heated district of the 



28-PROC. BIOL. Soc. WASH., VOL. XIX, 1906. 



