426 



ROSACEAE 



10. Ivesia pygmaea A. Gray. Dwarf Ivesia. Fig. 2407. 



Ivesia pygmaea A. Gray, Proc. Amer. Acad. 6: 531. 1865. 

 Ivesia Gordonii var. pygmaea S. Wats. Bot. Calif. 1 : 183. 1876. 

 Potentilla decipiens Greene, Pittonia 1: 106, as to synonyms. 1887. 

 Horkelia pygmaea Rydb. Mem. Dept. Bot. Columbia Univ. 2: 152. 1898. 

 Ivesia chaetophora Rydb. N. Amer. Fl. 22 : 290. 1908. 



Stems scapose, 4-12 cm. high, glandular-puberulent. Basal leaves numerous, 2-5 cm. long, 

 finely glandular-puberulent ; leaflets numerous, densely crowded, 1-2 mm. long, divided to the 

 base into oblong or oval thick segments, usually tipped with bristles ; cyme subcapitate ; hypan- 

 thium glandular-hirsute, 4 mm. broad ; petals yellow, obovate, slightly exceeding the triangular- 

 lanceolate sepals ; stamens 10. 



Rocky alpine slopes, Arctic- Alpine Zone; Sierra Nevada, California, and western Nevada. Type locality: 

 Sierra Nevada. July-Aug. 



11. Ivesia Muirii A. Gray. Muir's Ivesia. Fig. 2408. 



Ivesia Muirii A. Gray, Proc. Amer. Acad. 8: 627. 1873. 



Potentilla Muirii Greene, Pittonia 1 : 106. 1887. 



Horkelia Muirii Rydb. Mem. Dept. Bot. Columbia Univ. 2: 148. 1898. 



Horkelia Chandleri Rydb. Bull. Torrey Club 28: 177. 1901. 



Ivesia Chandleri Rydb. N. Amer. Fl. 22: 286. 1908. 



Stem from a short cespitose caudex, 2-16 cm. high, simple, silky-villous. Basal leaves, 2-5 

 cm. long, densely white-silky, terete and wormlike from the numerous small densely imbricate 

 leaflets ; hypanthium cupulate, 3 mm. broad ; sepals triangular-ovate, 2 mm. long, a third longer 

 than the linear bractlets ; petals yellow, linear, 1 . 5 mm. long ; stamens mostly 5. 



Alpine peaks above timber line, Boreal Zones: Sierra Nevada crest from Tuolumne and Mono Counties to 

 Fresno County, California. Type locality: Mount Hoffmann, Sierra Nevada, California. July-Aug. 



12. Ivesia Webberi A. Gray. Webber's Ivesia. Fig. 2409. 



Ivesia Webberi A. Gray, Proc. Amer. Acad. 10: 71. 1874. 



Potentilla Webberi Greene, Pittonia 1: 105. 1887. 



Horkelia Webberi Rydb. Mem. Dept. Bot. Columbia Univ. 2: 149. 1898. 



Stems several from a cespitose caudex, decumbent, 5-15 cm. long, glabrate. Basal leaves 

 3-4 cm. long, the petioles with long fine silky hairs; leaflets 8-10 pairs, grayish silky but not 

 densely so, 1 cm. long, divided to the base into linear or lanceolate acute segments; cyme sub- 

 capitate ; hypanthium cupulate, 4 cm. broad ; sepals ovate or ovate-lanceolate, 4 mm. long, exceed- 

 ing the linear bractlets ; petals yellow, oblanceolate, scarcely as long as the sepals ; stamens 5. 



Dry barren ground, Arid Transition and Canadian Zones; northern Sierra Nevada, especially the eastern 

 slopes of Plumas and Sierra Counties, California, also Washoe County, western Nevada. Type locality: Sierra 

 Valley, California. June— Aug. 



13. Ivesia Tweedy i Rydb. Tweedy 's Ivesia. Fig. 2410. 



Ivesia Tweedyi Rydb. N. Amer. Fl. 22: 287. 1908. 

 Horkelia Tweedyi Nels. & Macbr. Bot. Gaz. 61: 31. 1916. 



Stems several, decumbent or ascending from a cespitose caudex, 1-2 dm. high, glandular- 

 puberulent. Basal leaves numerous, 5-8 cm. long; leaflets 15-20 pairs, 4-8 mm. long, divided to 

 the base into 3-5 linear or oblong-oblanceolate segments, glandular-puberulent ; cymes open, 

 with ascending branches ; hypanthium 3 mm. broad, cupulate, slightly short-villous and glandular- 



2408 

 2408. Ivesia Muirii 



2409. Ivesia Webberi 



2410. Ivesia Tweedyi 



