116 CALIFORNIA ACADEMY OF SCIENCES. 



or more or less hirsute to very densely white- or rusty- 

 tomeutose on the lower surface of the leaves. The inflor- 

 escence is intermediate between that of the preceding and 

 following groups of species. In some of the rather slender- 

 stemmed plants that I regard as most typical, the twigs are 

 very rough with crowded small warts. Probably one or 

 more species may ultimately be separated out, and it is not 

 certain that a number of specimens now referred here do 

 not really belong to divaricatus on the one hand, or Jiirsutus 

 on the other. 



The dentatuH group is one of the best circumscribed, but 

 it is not less puzzling than others, for it is doubtful whether 

 the forms it comprises are best described as species or va- 

 rieties. Lobhianus is chiefly characterized by its conspicu- 

 ously unequal leaves — those on the primary shoots 25 mm. 

 long, mostly acute at both ends, the larger 3-nerved. 



While I have scarcely felt that this form and floribimdus 

 are worthy of specific rank, I have pretty confidently sep- 

 arated out the plant with rather broad hairj^ leaves, deeply 

 furrowed over the veins. It is known to me only from two 

 flowering specimens in the Gray herbarium, collected at 

 different places. 



In Cerastes the species are quite as perplexing as in 

 EucEA-NOTHUs, and the difiiculty of separating them is in- 

 creased by the occurrence of what appear to be hybrids. 

 This is especially true of prostratiis and cuneatus, typically 

 very distinct in habit, foliage, flowers and fruit; but nu- 

 merous specimens have been collected over a large area, 

 showing various combinations of the characters of both. So 

 marked are these that Mr. Thomas Howell writes me that 

 from his field observations he is disposed to regard prostra- 

 tiis as only a variety of cuneatus.* 



On these supposed hybrids, see Garden and Forest, i. 7. 



