564 PROCEEDINGS OF THE AMERICAN ACADEMY. 



form. Great variation and closely related species indicate a recent 

 genus still in process of evolution. The line separating Orthocarpus 

 from Castilleja is not definitely fixed, and the species on the border 

 may suffer changes in name frequently. At present the tendency is 

 to remove all these doubtful species from Orthocarpus and include 

 them in Castilleja, thus leaving the former genus represented only by 

 annuals. The two genera are certainly very closely related, for there is 

 scarcely a character of Orthocarpus which cannot be found in some 

 species of Castilleja. Indeed, it is doubtful if the differences between 

 the two genera are much more pronounced than are the differences be- 

 tween some of the sections of Castilleja. The last enumeration of the 

 Mexican and Central- American species of Castilleja was in 188] -1882, 

 when Hemsley enumerated 26 species (Biol. Cent. -Am. Bot. ii. 459-463). 

 Since then great activity has prevailed in the biological exploration of 

 Mexico and Central America, and specimens of Castilleja have been 

 accumulating in all the large herbaria. The present paper is based upon 

 the specimens in the Gray Herbarium and some from the herbarium of 

 the U. S. National Museum. Besides the key a short diagnosis of 

 each species has been added, sometimes modified from the original 

 description and sometimes quoted. 



Sectio I. Epichroma Benth. in DC. Prodr. x. 528 (1846). 



Calyx vix fissus, breviter et obtuse sinuato-lobatus. Folia pinnati- 

 secta ; rhachi et laciniis filiformibus vel anguste linearibus. Folia 

 fioralia caulinis minora et concolora. Flores laxe spicati vel racemosi. 

 Annua. 



Flores 2.5 cm. longi. Calyx coccineus infundibuliformis. Galea flava a basi 

 exserta 1. C. tenuifolia. 



Flores 2 cm. longi. Calyx flavus. Galea flava exserta 2. C. aurea. 



Flores 1.5 cm. longi. Calyx viridi-purpureus. Galea viridi-flava paulo 

 exserta 3. C. gracilis. 



Sectio II. Euchroma (Nutt.) Benth. 1. c. 529. Euchroma Nutt. 



Gen. ii. 54 (1818). 



Calyx in duas partes subaequaliter fissus, segmentis integris vel 

 obtuse bilobatis vel acute bifidis. Folia fioralia caulinis latiora, apice 

 dilatata et semper colorata. Flores et bracteae in spicis confertae, 

 demum interruptae. 



