OP ARTS AND SCIENCES. 295 



stipitate. The long divisions of the corona are fully 2 lines in length, 

 ^ of a line wide, erect, in the just opening blossom nearly equalling 

 thecorolhi; they are accordingly very conspicuous: the five subuhite 

 processes opposite the anthers are inconspicuous and are somewhat 

 incurved. The stigmatic disk is smaller in proportion than in most 

 Gonolubea;, and does not at all cover the anthers : these are wiiolly 

 destitute of scarious apical appendages, and the pollinia arc obviously 

 pendulous and disposed to be vertical. Still the affinity of this plant 

 seems manifestly to be with Gonolobus and PolysUmina. It cannot 

 well be referred to the latter, although it may be near it. Tlie 

 generic name (i/xdvro9, cn-e/xjua) refers to the strap-shaped lobes of the 

 corona. 



ROTIIROCKIA, Nov. Gen. Asclepiadacearum. 



Calyx 5-partitus, intus squamellis minimis 3-4 instructus. Corolla 

 rotata, profunde 5-fida, lobis oblongis anguste dextrorsum convolutis. 

 Corona simplex, imte basi corolla3 et tubo stamineo inserta, 5-partita, 

 lobis antheris oppositis crassis subcuneatis vix cucullatis. Anthei'te 

 bi-eves : pollinia ovalia, sub ajwce caudicula3 brevi adfixa, pendula. 

 Stigma vertice in coluranam apice tricristatam producto. Folliculi 

 crassiusculi, acuminati, Iceves. Semina comosa. — Herba volubilis, 

 pubescens, basi sufFrutescens ; foliis oppositis cordatis acuminatis 

 longe petiolatis, petiolis ramisque paten ti-hirsutis ; cymis axillaribus 

 laxis bracteolatis demura racemiformibus ; corolla albida. 



RoTiiROCKiA CORDIFOLIA. — Southern Arizona (Catalina Moun- 

 tains, «S;c.), where it seems to have been first collected by Lenimon, in 

 April, 1881, in fruit only, and the specimens taken for RouUinia 

 nnifaria, perhaps distributed under that name: in 1884 collected by 

 Pringle, both in flower and in fruit, in Northwestern Sonora (along 

 with Hlmantostemma and Pringleophytum) in a range of rocky hills 

 southwest of Altar. 



The genus is dedicated to my friend and former pupil. Dr. J. Trimble 

 Rothrock, Professor of Botany in the University of Pennsylvania, at 

 Philadelphia, a keen botanist and zealous teacher, an explorer both in 

 Alaska and in Arizona, author of a Sketch of the Flora of Alaska, and 

 of the Botany of AYheeler's Report upon the U. S. Surveys of Arizona 

 and Southern California, and whose name it is well to commemorate 

 in an Arizono-Mexican genus. The plant seems most like Enslenia, 

 RouUinia, or the Endotropis section of Cynanchum. Its main pecu- 

 liarity is in the apical process of the stigma, a short and thick body 

 with dilated base, somewhat longer than the whole column, its apex 



