96 



A recent revision of this group by Dr. Aven Nelson ap- 

 peared'' in 1931. His treatment is not essentially different from 

 that of Elias Nelson, but he keys P. longijoUa as with "Leaves 

 3 mm. or more broad, 4-8 cm. long," and P. linearifolia as with 

 "Leaves 2 mm. or less broad, 3-6 cm. long." 



A prolonged study of this group has made clear that the 

 width of the leaf is a markedly variable character. A large 

 series of specimens shows a gradual progression from ones as 

 narrow as 0.5 mm. to those up to 3 mm. Even if 2 mm. is chosen 

 as an arbitrary division point, it will separate the plants into 

 two piles, but each of these will contain both glabrous and 

 pubescent plants. If the plants are sorted on the pubescence 

 character, particularly that of the calyx, the division into 

 groups is much more clear and convincing. Were other char- 

 acters correlated, it would be logical to maintain both as species, 

 as did Gray and E. Nelson. However, some collections show 

 intermediate conditions, even in the pubescence of the calyx. 

 One such from Palouse Falls, Washington, St. John & Pickett 

 6152, contained five branches with the glabrous calyces, five 

 with markedly hispidulous calyces, and one scarcely so. These 

 were growing side by side, were collected as one number, and 

 show a blending of the characters. The pubescence of the leaves 

 is usually similar to that of the calyces, but some specimens 

 recombine these characters. The ranges of the two plants are 

 nearly identical. 



There is also a glandular pubescent plant which has to be 

 considered. All in all, the writer is convinced that this group is 

 most truly classified as one species. Phlox longifolia Nutt., with 

 several varieties. 



Key to Phlox longifolia and its Varieties. 

 Plant not glandular pubescent, 



Calyx glabrous; leaves glabrous or with sparse basal ciliations. 



Phlox longifolia. 

 Calyx hirsute; leaves usually so, or puberulent. 



Var. linearifolia. 

 Plant glandular puberulent. Var. puberula. 



/ Phlox longifolia Nutt., Journ. Acad. Nat. Sci. Phila. 7: 



41-42, 1834. Perennial, 1-4 dm. tall; tap-root yellowish, elong- 



« Am. Journ. Bot. 18: 441-442, 1931. 



