64 PROCEEDINGS OF THE AMERICAN ACADEMY. 



In 1881 Hemsley ^ credited to Mexico 24 species of Pectis, though some 

 of them doubtless cannot stand. P. Liebmannii, Sch. Bip., one of the 

 best marked species of § Pectothrix, was described as new ; and since the 

 publication of Hemsley nine additional Mexican species have been de- 

 scribed. 



In 1883^ Dr. Gray discussed the genus Pectis, making many critical 

 notes upon the species. He at that time modified his division of the 

 genus, so that he recognized only three sections : — 



1. EuPECTis. Pappus paucipaleaceus, vel pauci-aristatus aristis setiformi- 

 bus, nunc ex aristis et paleolis paucis vel definitis constans, plerumque uniserialis. 



2. Pkctothkix. Pappus (saltern fl. disci) multisetosus, insequalis, ple- 

 rumque biserialis, setis interioribus validioribus quandoque aristiformibus inferne 

 sensiin latioribus nee vero paleaceis. 



3. Pectidium. Pappus bi-tricornis, nempe ex aristis paucissimis (1-4) 

 validis corneis saspius divergentibus. 



This division was followed in the Synoptical Flora, ^ where P. Rushyi, 

 Greene, from Arizona, was described as new. 



Two species, P. gibhosa and P. linearis, have been published in a recent 

 number of La Naturaleza ^ from old descriptions written by La Llave in 

 1832. These descriptions, however, contain so little of a specific nature 

 that it is impossible to tell from them alone what the plants may be. 



The genus Pectis is, as Dr. Gray has remarked, a very natural one ; in 

 fact, it presents such intergradations that it is diflScult to get a really satis- 

 factory basis for division into sections. Habital characters in such a group, 

 with many short-lived annuals, are very unsatisfactory : in many cases 

 plants ordinarily perennial with a suffruticose base may develop as annuals. 

 The color of the rays, the number and length of the basal setae of the 

 leaves, and the distribution of glands, are all characters so inconstant as 

 to be of only minor importance. The only character which seems suffi- 

 ciently constant, at least for the larger divisions into subgenera, is in the 

 pappus, and even that presents some obstructions to the making of clearly 

 defined groups. 



In attempting to group all the United States and Mexican species, it 

 seems that the best results are attained by a compromise between Dr. 

 Gray's recent treatment of the genus (Proc. Amer. Acad. xix. 43-48), 

 and his earlier division of it in Plantre Wrightianae (i. 83). The sub- 

 genus Heteropectis is sufficiently unique, apparently, in its retrorsely barbed 



J Biol. Centr.-Am. Bot. ii. 224-227. ^ Gray, Syn. Fl. i. pt. 1, 360. 



2 Proc. Am. Acad. xix. 43-48. ^ La Nat. vii. Append. 84. 



