54 Rydberg : Rocky Mountain flora 



ACERACEAE 



Negundo fRay) Ludwig-Boehmer, Def. PI. 508. 1760 

 Professor Nieuwland in the American Midland Naturalist* 

 discussed the North American species of box-elder. He used the 

 name Rulac, believing in a pre-Linnaean priority for genera. As 

 both the Vienna Rules and the American Code have adopted 1753 

 as the starting point for botanical nomenclature, few will follow 

 him in the names adopted. If our box-elders are regarded as 

 generically distinct from the maples, we must use the name 

 Negundo. Professor Nieuwland recognizes six species. I think 

 there should be recognized eight species in North America. The 

 Texan form, Riilac calif ornica texana Pax, is well distinct from 

 Negundo californicum, Professor Nieuwland having overlooked the 

 difference in the fruit, which in the Texan species agrees more with 

 our eastern box-elder and was included in it by Dr. Britton. 

 The following key was prepared by me over two years ago and two 

 new species were named in manuscript. One of these has been 

 described by Professor Nieuwland under the name Rulac Nuttallii; 

 a description of the other is given below. I publish here the key, 

 as several of the characters have not been pointed out by Professor 

 Nieuwland. 



Branches of the season glabrous or with a few scattered ap- 

 pressed haiis; anthers acute, tapering into a tip V4-H 

 mm. long, formed by the produced connective (in the 

 first species unknown). 

 Fruiting pedicels glabrous, the lower 5-8 cm. long, very 

 slender: fruit glabrous, contracted below into a short 

 stipe. I. N. orizahense. 



Fruiting pedicels sparingly pilose: the lower 2-3 cm. long. 

 Ovary and fruit finely pubescent; the latter some- 

 times becoming glabrate in age, distinctly con- 

 stricted below into a narrow stipe-like base; leaflets 

 broad, toothed, rarely lobed. 2. A''. Negundo. 



Ovary and fruit glabrous; the latter slightly or usually 

 not at all constricted below; leaflets usually lobed, 

 with hair-tufts in the axils of the veins. 3. A^. Nuttallii. 



Branches of the season densely velutinous with short spreading 

 hairs; anthers obtuse, merely mucronate. 

 Leaflets coarsely dentate or lobed; style evident but short. 

 Fruit distinctly constricted at the base into a short 

 stipe, densely and minutely pubescent; leaflets 



*\'ol. 2: 129-140. 1911. 



