184 MR. NUTTALL'S DESCRIPTIONS OF NEW 



PEUCEDANUM. 



§. *Peucelimum. Carpels with two of the lateral ribs undulately winged ; vittse 

 indistinct, one or two ; commissure . 



P. *ABROTANiFOLiuM. Somewhat pubescent, branching from the base ; leaves ternately decompound, 

 ultimate segments narrowly linear ; involucels about seven to nine-leaved, the leaflets palmate, 

 distinct, petiolulate, nearly as long as the umbellet; fruit obovate-elliptical, with a broad, winged 

 margin, and some of the inner ribs with undulated membranaceous margins. 



Like many other plants of this family, there is so striking a resemblance betwixt 

 the present species and the P. caruijolium, that at first I imagined them to be the 

 same, yet the character of the involucrum and the fruit is so wholly different, indeed, 

 from the rest of the genus, as to require a particular section. The present is also a 

 much larger plant than P. caruifolium, eighteen inches to two feet high ; the leaves 

 multifid, with narrow linear acute segments; petioles very short with an inflated 

 base. The plant branching from the base into two or three divisions, umbel 

 subtended in the two instances out of three with a proper multifid leaf; rays of the 

 umbel ten or fourteen, with several short abortive or masculine umbelets in the 

 centre of the umbel ; several abortive flowers in each, umbelet. Flowers yellow. 



Hab. Pueblo de los Angeles, Upper California. (A single specimen, not far 

 enough advanced to ascertain the ultimate character of the fruit. ) 



PTEROCHITON. 



P. CANESCENS. In fruit. P. occideniale. Torrey in Frem. Journ. p. 318. 

 CalUgonum canescens. Pursh. Flor. Am. ii. p. 370, excluding the synonym Atriplex 

 canescens. Nutt. Gen. Am. i. p. 197. 



This plant in several collections to which it was communicated, was marked 

 Pterocarya canescens, as far back as 1836. At the same time 1 marked in the 

 collection of the Academy of Natural Sciences and elsewhere, the " Pulpy leaved 

 Thorn " of Lewis and Clark, by the name of " Sarcacanthus," the Sarcohatis of 

 Nees, and Fremontia of Torrey ; by the names so marked I intended to have 

 published these plants. Pursh's CalUgonum, which I mistook for my Atriplex 

 canescens, must have been in the collection of Lewis and Clarke, as I did not meet 

 with it on the borders of the Missouri. In the same journey I collected very perfect 

 specimens of the plant since called Graijia, which I marked in the collection of the 

 Academy Psilocarpus. 



Hab. In the Rocky Mountains of California abundant, and also towards the 

 sources of the Platte, where it forms a shrub three or four feet high. 



