THE GENUS LEIOSTEMON. 333 



T. OBSCUBA. Ptelea obscura, Greene, 1. c. Pericarp large, 

 subquadrate-oval, its margin obtuse. 



Interior of northern L. Calif., near Santo Tomas. 



T. NUCIEBKA. Ptelea nucifera, Greene, 1. c. Fruit large, 

 oval, sharply carinate all around the margin. 



Near a desert water hole, middle of L. Calif., inland. 



The Qenus Leiostemon. 



When nearly thirty years since in New Mexico I for the first 

 time saw the type of this genus, not knowing its name, I 

 regarded it as possibly a Gerardia, neyer thinking of Peniste- 

 mon at all in connection with it, so far remoyed as it is in habit 

 and in the structure of its flower from the last named. I was 

 therefore not well satisfied when 1 learned that its only name in 

 botany was Pentstemon ambigkus; the trivial name also telling the 

 tale of Torrey's own doubt about the reasonableness of the 

 placing of it as a species of Pentstemon. 



Within the last year, having been led to examine and com- 

 pare a series of specimens from different places, I reached the 

 decision that the type ought to be excluded from Pentstemon and 

 given the rank of a genus. I could not readily invent a pleasing 

 generic name for it, and the subject passed out of my mind. 

 This may have been fortunate; for, in reading lately some 

 botanical articles by Rafinesque in the Atlantic Journal, I came 

 upon his establishment of this type in the rank it demands, and 

 with a name that may easily pass without any objection that I 

 can see. 



The species of Leiostemon' seem to me to be two at the least, 

 with possibly as many more. 



L. AMBiGUUS. Pentstemon ambiguus, Torr. L. purpureu&r 

 Eaf. 



L. Thukberi. Pentstemon Thm^X'^- Torr.^ 



