130 BOTANY. 



brandies of the style exserted and slightly recurved ; remaining florets per- 

 fect, corolla 5-toothed, branches of the style included, truncate and with a 

 few cilise at the middle of the ends; immature achenia oblong-top-shaped; 

 pappus none. — "With much the appearance of Artemisia cana, but the broad- 

 topped achenia are characteristic of Tanacetum. Whether this is to be re- 

 ferred to the section Sphceromeria or not, must be decided by the examina- 

 tion of maturer specimens. Limestone rocks at the mouth of a canon in the 

 East Humboldt Mountains, Nevada; -6,500 feet elevation; July. Plate 

 XIX. Fig. 8. Portion of a plant ; natural size. Fig. 9. Receptacle. Fig. 

 10. Involucral scale ; each enlarged four diameters. Fig. 11. Outer pistillate 

 fertile flower. Fig. 12. Inner perfect flower ; each enlarged eight diameters. 

 Fig. 13. Style of perfect flower. Fig. 14. Stamen; each enlarged twelve 

 diameters. (631.) 



Tanacetum diversifolium. SuffVuticose, glabrous, branched from the 

 base ; branches 8-15' high, leafy to the top ; leaves 1-2' long, ^-1" wide, 

 sessile, narrowly linear, 1-nerved, or pinnatifid with 1-4 linear-oblong 

 1-nerved divisions ; heads small, sub-globose, congested or laxly disposed in 

 terminal corymbs; peduncles and involucres puberulent, the latter cup-shaped, 

 of 12-15 oval scarious-margined concave scales ; receptacle conical; florets 

 60-70 ; outer pistillate ones 8-10, with a 3-4-lobed corolla a little shorter 

 than the style ; inner perfect ones, 5-lobed branches of the style very mi- 

 nutely penicillate at the broad truncate extremities; achenia oblong, crowned 

 with a sHghtly elevated ring. — A dense much-branched plant, shrubby at the 

 base, in habit not unlike some narrow-leaved Linosyris. Central flowers 

 with a rudimentary seed, but possibly infertile. Canons of Cottonwood 

 Creek and American Fork, in the Wahsatch; 6,000 feet elevation; July, 

 August. Plate XIX. Fig. 1. A single stem; natural size. Fig. 2. Eecep- 

 tacle. Fig. 3. Involucral scale ; each enlarged four times. Fig. 4. An 

 outer pistillate fertile flower. Fig. 5. An inner perfect flower ; each enlarged 

 eight times. Fig. 6. Stamen. Fig. 7. Style of inner flower ; each enlarged 

 twelve times. (632.) 



Artemisia spinescens. {Picrothamnus desertorwn, Nutt.) Low, fru- 

 tescent, densely-branched, white-tomentose ; leaves scarcely 3" long, pedately 

 3-5-parted, the divisions 3-lobed, lobes oblong ; heads rather small, globose, 

 in short axillary racemes or spikes, the rachis persistent 2-3 years and spin- 

 escent ; involucral scales 5-6, obovate, obtuse, concave ; receptacle small, 



