1904.] NATURAL SCIENCES OF PHILADELPHIA. 113 



that he could not agree with this, but that I apparently had the long- 

 lost R. arkansana Porter, only certainly known bj^ the original col- 

 lection by Brandegee. As this seems reasonable, I provisionally call 

 my plant arkansana, the more willingly since the name has priority over 

 jendleri, supposing them to refer to one species. The material described 

 above grows by a small irrigation ditch in open unshaded groimd, which 

 except for the ditch is very drj^ On August 13 a fruiting bush of the 

 same species was found close to the Pecos river, more or less in the 

 shade. It possessed the following characters : 



Fruit very shiny, smooth, globose (long. 9^, lat. 9, to long. 12, lat. 

 10 mm.), slightly longer than broad, without the slightest indication of 

 a neck. Sepals erect, 15 mm. long, some with linear lobes ; the margins 

 woolly, the dorsal sm-face with loose arachnoid hairs and scattered 

 gland-hairs. Peduncles perfectly glabrous and somewhat glaucous, 

 5-10 mm. long. Infrastipular spines variable, present or absent. 

 Spines on flowering branchlets straight. Stipules very narrow, diam- 

 eter 2-4 mm., beneath with loose arachnoid hairs and short reddish- 

 gland-hairs; petioles minutely pubescent, with scattered short red 

 gland-hairs; leaflets 7 to 9, rather narrow {e.g., long. 23, lat. 12^ mm.), 

 resin-dotted beneath, simply toothed, edges not glandular, lateral 

 leaflets briefly petiolulate. A low bush. 



It will be seen that this in many respects approaches R. pccosensis. 

 R. arkansana, var. a, was infested by an aphid, which appears to be 

 identical with Myzus rosarum Walker. 



In order to appreciate the characters of the Pecos roses, it is neces- 

 sary to review the described North American species of the same group, 

 and also certain forms occurring in other parts of Xew ^lexico. 



The Described Species. 

 (1) Rosa grosseserrata E. Nelson. 



Bot. Gaz., August, 1900, p. 119. 



Type from the Yellowstone Park, collected in fruit. I am indebted 

 to Prof. Aven Nelson for a specimen. This is quite like typical R. 

 pecosensis in the serrations and pubescence of the leaves ; the serrations 

 are long and pointed, perfectly simple and not glandular. The stipules 

 are broader than in pecosensis. The fruit is considerably larger, about 

 12 mm. diameter. The author of this species-name thinks the plant 

 is intermediate between R. pisocarpa and R. icoodsii, and I believe 

 that it is not so close to pecosensis as the resemblance of the leaves 

 might suggest. The absence of paired infrastipular spines or prickles 

 seems to remove R. grosseserrata from the vicinity of R. pisocarpa and 

 S 



