60 PROCEEDINGS OP THE AMERICAN ACADEMY 



uiulerstanding of the characters. The changes and additions are 

 briefly exhibited in the following synopsis. 



§ 1. Allosekis (Gray, Proc. Am. Acad, vi., in part). Heads of the 

 largest, about 12-flowered: involucre obviously imbricated: recep- 



-w -w Folia oblonga seu ovata, reticulata, modo generis crebe denticulata vel 



dentata, 



= Basi sessili baud angustata aut truncata aut subcordata sed parura amplexi- 

 cauli : caulis ercctus : rami ad apicetn aperte cymoso-pleiocephali : involucrum 

 pauciseriale, bracteis angusto-oblongis obtusis vel intimis obtusiusculis. 

 P. Wrightii, Gray, Pi. Wriglit. i. 127. P. Arizonica, Gray, Bot. Calif, i. 422, 



forma rigidior. P. Conlteri, pro parte, Gray, Proc. Am. Acad. xv. 40. Texas 



to Arizona, and a ratlier rigid and small-leaved form extending into Mexico to 



San Luis Potosi, Schaffner, Parry <J- Palmer, no. 547 in part. 



= = Basi cordata vel sagittata amplexioauli: caulis gracilis, patenti-ramosus ; 

 ramis oligoceplialis ; involucrum circiter quadriseriale, 



a. Campanulatura pluriflorura. 



P. CARPHOLEns [Acourtia carphulepis, Schultz Bip. in coll. Licbm.). Ramis 

 flexuosis patentissimis; foliis laite-viridibus ovatis obiongisve siepe acuminatis 

 quandoque sinuatis; capitulis in ramulos breves foliatos paucis brcvissinie peti- 

 olatis semipollicaribus circiter 10-floris ; involucri bracteis obtusissimis ovalibus 

 oblongisque apice nunc purpureo tinctis. — P. patens var. fi & var. y, Gray, PI. 

 Wrigbt. 1. c. Cliiapas, &c., S. Mexico, Linden, 439, Galcoiti, 2001, Liebman, 351 

 in part, Ghiesbreght, 525, tlie latter in pine forests. 



P. PATENS, Gray. Glaucescens ; ramis virgato-paniculatis ; foliis oblongis 

 obtusis mucronato-denticulatis; capitulis niajoribus §-:]-polli('aribus pedunculos 

 graciles bracteolatos terminantibus circa 20-floris ; involucri bracteis ovato- et 

 lanceolato-oblongis obtusiusculis. — Acourtia formosa, Schultz Bip. in Bot. Herald, 

 t. 56, & Trixis patens, 1. c. p. 315. — N. W. Mexico, Seeviann. 



b. Involucrum cylindraceum 5-florum. 

 P. DuGESii. Foliis ramisque {\exnosis P. carpholepidis ; capitulis ultra-semi- 

 pollicaribus in glomerulum axillare sa>pius brevipeduiiculatum basi 1-2-phyllura 

 congestis ; involucri 5-flori bracteis latiuscule linearibus mucronato-apiculatis, 

 extimis parvulis ovato-oblongis niagis acuminatis; floribus purpureis. — Gua- 

 naxuato, Duges. A flowering branch onl}'. 



^- 4- 4- Involucrum arctius imbricatum, bracteis firmioribus ovalibus obion- 

 gisve obtusis nunc mucronulatis : capitula magis fasciculato-congesta plerum- 

 que sessilia, 



++ 8-15-flora : folia basi sat lata truncata, subcordata, vel auriculata. 



P. ADNATA, Graj'', PI. "Wright, i. 127. Subglanduloso- vel viscidulo-pubcrula ; 

 caule ramisque usque ad capitula pauciuscula glomerulato-congesta jequaliter 

 foliosis : foliis Chartaceis ovatis ovalibusque, basi lata auriculis sjepius adna- 

 tis; involucro cylindraceo 8-11-floro. — Dumeriliu Alamaui, DC. Prodr. vii. 07, 

 therefore Perezia Alamaui, Ilemsl. Biol. Centr.-Am. Bot. ii. 255. — CHiiesbreght's 

 plant (the first to be described under this genus) has all the cauline leaves with 



