140 GENUS ABTEMISIA. 



green as in specimens from the type locality of rothrocki, and in one from Crested Butte, Colorado {Baker 810) 

 the involucres are essentially glabrous, except for the short outer bracts. In the former collection the (young) 

 involucres are gray-tomentose, in the latter the foliage is densely cinereous. These perplexing combinations, 

 together with the fact that Sierra Nevadan plants are for the most part decidedly cinereous-canescent and 

 scarcely viscidulous, render impossible the recognition of spidformis. (See further under No. 18 of this list.) 



8. A. SPiciFORMis var. lonqiloba Osterhout, Muhlenbergia 4:69, 1908. — A low form of A. tridentata roth- 

 rocki with densely canescent foliage, the leaves 3-cleft for nearly one-half their length. Plants about 3 dm. high. 

 Scarcely differs from subspecies trifida, except in size of head and number of flowers. Type locality, Sulphur 

 Springs, Colorado. 



9. A. TRIDENTATA ANGUSTiFOLiA Gray, Proc. Am. Acad. 19:49, 1883. — A narrow-leaved form of A. tridenr- 

 lata typica. Lower leaves spatulate-linear and scarcely 3-toothed at the rounded apex ; upper entire and linear. 

 Original distribution given as southern Idaho and western Nevada to the Mojave Desert and the southern 

 borders of California. 



10. A. TRIDENTATA ARBUscuLA, but with the leaves deeply cleft as in No. 8 of this list and in subspecies 

 trifida. Best represented by plants from Placer County, California, Heller 12914 (UC). 



11. A. TRIDENTATA NOVA, but the involucrcs canescently tomentulose and the stem commonly reddish. It 

 seems better to accept this as a minor variation of subspecies rwva rather than to give it subspecific rank, partly 

 because of the presence of intergrading forms (Mount Irish, Nevada, Purpus 6S3S UC), partly because the short 

 outer bracts are always canescent even in genuine nova, and partly because of the demonstrated variability of 

 this character in related subspecies, for example rothrocki. This form sometimes forms pure stands in eastern 

 California and eastern Oregon in regions where the surrounding vegetation is composed chiefly of subspecies 

 typica. The line between the two is often very sharp, the low reddish-twigged noya-like plant occupying the less 

 favorable locations and persisting because of repeated fires or grazing, if not actually produced by them. Typi- 

 cal of this form is a collection from between Bodie and Bridgeport, Mono County, California, August 18, 1898, 

 Congdon (UC). It is common on upper slopes between Mono Lake and Bridgeport (Hall 11696, UC). Also in 

 eastern Lassen County, California {Hall 11674, UC) and in eastern Oregon (near Antone, Loflfield 2113, UC). 

 Almost the same thing, but the slender inflorescences more branched, comes from draws south of Laramie, 

 Wyoming (September 9, 1919, Hall, UC). 



12. A. TRIDENTATA NOVA, but with dark foliage, this appearing almost black as compared with other forms. 

 Plants low and with narrow inflorescences. Apparently a more palatable strain kept low by grazing. Occurs 

 in southern Idaho and elsewhere. 



13. A. TRIDENTATA ROTHROCKI, but some of the leaves cleft one-third their length. Volcano Meadows, 

 southern Sierra Nevada, Hall and Babcock 5490 (UC). 



14. A. TRIDENTATA TYPICA, but with the branches of the inflorescence drooping. The best examples are 

 large shrubs growing in moist, sandy soil. Found especially in northwestern New Mexico {Hall 11124). Well 

 worthy of cultivation as an oranmental shrub if the character persists. 



15. A. TRIDENTATA TYPICA, but much dwarfed, usually as a result of competition with grasses. Resembles 

 subspecies nova in its stature, but lacks its slender habit, narrow inflorescence, and smooth involucres. Common 

 in Wyoming, for example, west of Bosler, September 10, 1919, Clements (UC). 



16. A. TRIFIDA Nuttall, Trans. Am. Phil. Soc. II, 7:398, 1841.— A. tridentata trifida. 



17. A. TRIPARTITA Rydberg, Mem. N. Y. Bot. Card. 1:432, 1900. — Based upon A. trifida Nuttall, here 

 reduced to a subspecies of A. tridentata. The specific name was changed by Rydberg because of the earlier 

 A. trifida Turczaninov, 1832, an untenable species. 



18. A. VASEYANA Rydberg, N. Am. Fl. 34:283, 1916. — A. tridentata rothrocki. Separated by Rydberg 

 chiefly on its broadly ovate outer bracts, which are less than half as long as the innermost, rothrocki being 

 described as having one of the outer bracts often a little foliaceous, the others ovate, acute, and half as long as 

 the innermost. The slight herbaceous elongation of outermost bracts is common in all of the subspecies and is 

 so variable as to suggest a correlation with factors affecting growth. A careful comparison has been made 

 between the types of the two "species." If the outer bracts are broader and more obtuse in vaseyana, they are 

 not convincingly so and they are no shorter in proportion to the inner ones. They are quite canescent as 

 contrasted with the nearly glabrous bracts of the type of rothrocki, but the lack of constancy in this feature has 

 been pointed out under A. spidformis. Its use would necessitate the extension of the range of vaseyana to the 

 type locality of rothrocki (Univ. Calif. Herb. 202229). The number of flowers in the head and the height of the 

 involucre do not serve, as is shown in Table 14, where the type of vaseyana and other specimens from its region 

 are entered. It would seem, therefore, that if vaseyana can be recognized at all, it must be on its canescent and 

 slightly broader outer bracts, and, if further collections substantiate the measurements given in the table, on 

 its narrower heads. Even as thus defined, the range must be extended to include most of the Sierra Nevada, 

 and here spidformis must also be admitted, because of plants with acutish but decidedly canescent bracts (for 

 example. Bear Valley, on road to Tahoe, September 9, 1888, SonTie). It is thus seen that these forms can not 

 be correlated with geographic distribution, except that genuine rothrocki is closely confined to the vicinity of its 

 type locality. The type locality of vaseyana is Washington. 



