OF ARTS AND SCIENCES. 333 



X. 



REVTSTON OF THE GENUS CEANOTHUS, AND DE- 

 SCRIPTIONS OF NEW PLANTS, 



WITH A SYNOPSIS OF THE WESTERN SPECIES OF SILENE. 



By Serexo Watson. 



Kead, March 9, 1875. 



1. Revision of the Genus Ceanothus. 



Some of the species of this exclusively American genus are well 

 marked and readily distinguished, but the larger number are defined 

 with difficulty, and the value of the specific distinctions must still be 

 considered in some cases as uncertain. It would be easy to increase 

 the number of nominal sjiecies, as, on the other hand, with aj^parent 

 reason, to considerably reduce them. But while endeavoring to give a 

 nearly uniform value to the several characters, taking at the same time 

 into consideration our impei'fect knowledge of some of the forms, it has 

 seemed best to retain as probably distinct some which seemingly run 

 together, and at the same time to avoid as far as possible proposing new 

 species. The following arrangement is as satisfactory as it could be 

 made with present material and information. 



§ 1. EUCEANOTHUS. Leaves all alternate, 3-nerved or j^innately 

 veined, glandular-toothed or entire ; fruit not crested. 



* Leaves 3-nerved from the base. 



•1— Erect shrubs, the branches not rigidly divaricate nor spiny ; inflo- 

 rescence thyrsoid ; leaves usually large, serrate except in (5). 



a. Low (1-3 feet high) ; flowers white, or sometimes light blue 

 in (5). 



1. C.Americana, Linn. More or less villous-pubescent ; leaves 

 thin, ovate or oblong-ovate, 1 i— 2 J inches long, on short petioles 2-6 

 lines long ; peduncles elongated. — From the Atlantic to Winnipeg 

 Valley, Iowa and Texas. 



