58 PROCEEDINGS OP THE AMERICAN ACADEMY 



Cuernavaca, Mexico, coll. Biliinek (October, 18GG), no. 512. Ex herb. 

 Cosson. 



Pkuezia, Lag. The section Acourtia, to which all the Mexican 

 and North American species belong, is well marked by its homo- 

 morphous flowers, even the marginal corollas having the three-toothed 

 outer lip little if at all longer than the two-parted inner lip. True 

 Perczia consists of the South American species, with the inner lobes 

 much shorter than the lijjuliform outer lip. * 



o 



* PEREZIA, § ACOURTIA. Key to the N. American and Mexican Species. 



§ 1. ScaposoE. 

 P. RUNCiNATA, Lag. ex Don. 

 P. NUDiCAULis, Gray, PI. Wright, i. P27. 

 § 2. Name, ilicifuUce, capitulis ad apicem caulium vel ramorum solitaris sessilibus. 

 P. NANA, Gray, PI. Fendl. i. 111. 

 P. Parryi, Gray, Proc. Am. Acad. xv. 40. 



§ 3. Caulescentes, foliatcn, sat altce, 



* Capitulum solitarium, poUicem altuni ct latum, crasso-pedunculatum in caule 

 robusto : involucri sublicmisphajrici bracteae exteriores ovataj, coriaccas, majus- 

 culse, hi.xaj, interioribus latioros et paullo breviores. 



P. WisLizENi, Gray, Pi. Fendl. 1. c, PI. Wright, i. 126. 



* * Capitula pauca vel spar-sa, pollicaria vel ultrapollicaria : involucri turbinati 

 bracteae homoniorplia;, angustae, acutissimaj, exteriores gradatim breviores. 



P. FORMOSA. P. turbinata, Gray, PI. Wriglit. 1. c.,non Llav. & Lex. Acourtia 

 formosa, Don, Trans. Linn. Soc. xvi. 204. A. macroccphala &, Trixis turbinata, 

 Scliultz Bip. in Seem. Bot. Herald, 305, t. 55. — Northern Mexico, Sesse ^ Mogino, 

 ex Don, Seemnun. 



P. TURUiNATA, Llav. & Lox. Nov. Veg. Dcscr. 25. Caule inferno asperulo su- 

 perne ramisque gracilibus laxe oligocephalis; foliis " coriaceo menibraiKiceis " 

 ovatis oblongisve amplexicaulibus creberrime spinuloso-dtnticulatis, majoribus 

 4-5-pollicaribus ; ramoaiibus parvis, summis in bracteas linoari-subulatis transe- 

 untibus ; pedunculis gracilibus; capitulis pollicaribus ; involucro 20-30- floro e 

 bracteis circiter triseralibus lanceohuis sensim acuniinatis sicco-chartaceis. — 

 Described here from abundant specimens collected by Schiffner (no. 220), on a 

 mountainside, in -the valley of Istlava, " Vallce de Mexico." Answers far bet- 

 ter to the characters given by Llave & Lexarsa tiian docs the preceding (to 

 which before knowing the present species I had assigned the name), and the 

 iiabitat accords better. For the P. formosa, as we must now name it, is known 

 only from the northern part of Mexico. 



* # * Capitula numcrosa, i'-poUicaria (8-12-flora), in thyrsum elongatura stric- 



tum foliosum aggregata: involucri bractca; angustas, acutissima;. 



P. THYRSOiDEA, Gray, Bot. Mex. Bound. 104. Viscidulo-puberula. 

 P. MoscuATA, Llav. & Lex. 1. c, if of the genus, may be placed here. 

 » » * » Capitula sat numerosa, vix ultra-senii])ollicaria, aut laxe aut glomera- 



tim cymoso-paniculata. 



