238 American Midland Naturalist Monograph No. 4 



Leaves spatula-shaped to reverse-lance-shaped, up to 2 mm. wide; flower 

 heads small, about % inch high; low shrubs mostly 4 to 12 

 inches high 3. C. depressus. 



Leaves narrowly linear or filiform; flower heads large and showy, about 



!/2 inch high; shrubs 1 to 3 feet high 4. C. pulchellus. 



Bracts of involucre not in sharply defined vertical rows; achenes mostly densely 

 hairy. 



Bracts of involucre short-pointed 5. C VtsciJiflorus. 



Bracts of involucre (or some of them) with long slender pwints 



- 6. C. Creenei. 



I. Parry Rabbitbrush (Chrysothamnus Parryi (Gray) Greene). — 

 Shrub 2/3 to 2 feet high, the branches densely covered with white or rarely 

 greenish wool when young, later becoming smooth and yellowish-green; bark 

 of main stems brown and stringy; leaves narrowly to broadly linear or some- 

 times broader above the middle, pointed at the tip, % to nearly 3 inches long, 

 usually exceeding the flower cluster, 1- to 3-nerved, only one nerve prominent; 

 flower heads erect, borne in narrowly oblong leafy clusters; flowers 10 to 20 

 in a head (or fewer in some varieties) ; involucre 1/3 to i^ inch high (or 

 higher in some varieties) ; bracts of involucre in more or less obvious vertical 

 rows, papery, the outer with slender green herbaceous tips; seed-like achenes 

 4-angled, covered with appressed hairs; occurs on hills and in dry valleys at 

 medium high elevations in the Rocky Mountains and in the Southwest. 



Field Guide to the Varieties 



Leaves mostly 1 to 'iYi inches long; flowers mostly 10 to 20 in a head 1. C. Parryi. 



Leaves Yi to 1-3/5 inches long; flowers mostly 5 to 7 (or 11) in a head. 



Leaves very narrow, '/g inch or less wide. 



Involucres !/2 to 5^ inch high, the bracts tending to be recurved at the tips 



1 a. Var. uevadensis. 



Involucres % to !/2 inch high, the bracts usually straight and erect at the 

 tips. 



Bracts of involucres 13 to 20, rather strongly keeled, the vertical rows 



obvious lb. Var. alteimaius. 



Bracts of involucres 9 to 12, not strongly keeled, the vertical rows 



rather obscure Ic. Var. vulcanicus. 



Leaves mostly 1/6 inch or more wide; rare species known only from Mono Pass 



on eastern boundary of Yosemite National Park Id. Var. Bolanderi. 



Occurrence (C. Parryi). — rocky mountain, rare, 7,200 to 8,500 feet: western 

 boundary of park; 2 miles southwest of Mount Bryant. MESA VERDE. z:oN, Coalpits 

 Wash, 3,600 feet. 



la. Nevada Rabbitbrush (Var. nevadensis (Gray) Jepson). — Usually 

 smaller than the species; leaves ^2 to li/^ inches long, 1 -nerved; flowers mostly 

 5 to 7 in a head, involucre y'2 to Yg inch high, the bracts tending to be re- 

 curved at the tips. 



Occurrence. — LASSEN, grand canyon, reported from the South Rim: Long Jim 

 Canyon, south of Shoshone Point, 6,800 feet. 



lb. Narrowleaf Rabbitbrush (Var. attenuatus (Jones) Hall). — Low 



