C. GREENEI. 191 



66. Chrysothamnus greenei filifolius (Rydberg). — Plant often taller and more 

 slender, bushy; leaves linear-filiform, usually 1 to 2 cm. long and less than 1 mm. wide, 

 often pale green; heads in compact cymes, sessile or subsessile; involucre 5 to 6 mm. 

 high, 2 mm. broad. (C. filifolius Rydberg, Bull. Torr. Club 28:503, 1901.) Range of 

 the species. Type locality, Granite, Colorado. Collections: Black Rock, New Mexico, 

 July 23, 1906, Wooton (US); Navajo Indian Reservation, Arizona, Standley 7365 (US). 

 (Additional collections are indicated in table 19.) 



MINOR VARIATIONS AND SYNONYMS. 



1. BiGELOViA QREENEi Gray, Proc. Am. Acad. 11:75, 1876. — C. greenei typicus. 



2. Chrysothamnus filifolius Rydberg, Bull. Terr. Club 28:503, 1901.— C. greenei filifolius. 



3. C. LARiciNUs Greene, Pittonia 5:110, 1903. — This appears to be C. greenei and probably subspecies ^Zi- 

 f alius. The type specimen can not be found at present. 



4. C. PUMILUS var. acuminatus Nelson, Bot. Gaz. 28:376, 1899. — C. greenei typicus. Type locality, La 

 Veta, Colorado. 



5. C. scoPARius Rydberg, I.e., 504. — C. greenei typicus. Reduced by Rydberg (Fl. Rocky Mts. 856, 1917). 

 Type locality, mesas, La Veta, Colorado. 



RELATIONSHIPS. 



In Gray's synopsis this species was placed next to ceruminosus on the strength of the 

 similarly tipped involucral bracts. This single similarity can not outweigh all of the 

 other evidence, such as the strongly pannose flexuous twigs and strongly keeled bracts of 

 ceruminosus, which plainly assign this latter to subspecies rank under C. nauseosus. C. 

 greenei, on the other hand, is of close affinity with C. visddiflorus, and the specimens in 

 herbaria are often ticketed as one of the varieties of that polymorphous species, usually 

 as variety stenophyllus. In common with these it has the low bushy habit, stifT very 

 brittle white-barked stems, similar involucres, and comparatively short style-append- 

 ages. It is probable that its similarity to stenophyllus is more than superficial and 

 indicates a close genetic relationship. However, it is well separated on the strength 

 of its attenuate or abruptly tipped involucral bracts and of the comparatively sharp 

 distinction between the tube and throat of the corolla. Furthermore, the style-appen- 

 dages in greenei are shorter in proportion to the length of the stigmatic portion than in all 

 but an occasional example of any subspecies of visddiflorus. In this respect it resembles 

 C. vaseyi, as will be further discussed under that species. 



The division of greenei into two subspecies is here given with some question as to its 

 value, but it follows the tendency of recent writers to give filifolius specific rank. The 

 first of these was Rydberg, who distinguished the segregates only on size of leaf and 

 heads and on the color of the former. This was done in distinguishing his new filifolius 

 from scoparius (Bull. Torr. Club 28:503, 1901), the latter since reduced by Rydberg to 

 greenei (Fl. Rocky Mts. 856, 1917). The gradation in these characters is indicated in 

 table 19, in which the length of the longest leaves, average width of mature middle leaves, 

 and the average height of fully developed involucres is given. 



From table 19, which includes all of the available material, it is seen that the speci- 

 mens may be divided into two groups based upon size of leaf and that the group with the 

 smaller leaves inhabits chiefly Utah and Nevada, a more arid region than Colorado, 

 whence come most of the collections of the larger-leaved group. The size of the involucre 

 is seen to vary irrespective of the leaves, although there is a tendency toward reduced 

 involucres in filifolius. Rydberg described typicus (under the synonym scoparius) as of 

 lighter color than the other, but the tendency is the other way, that is, the paler plants 

 usually belong to the more westerly filifolius. This is in keeping with the usual reduction 

 in chlorophyll as a species passes into the more arid Great Basin area. 



Additional characters have been introduced by Wooton and Standley (Contr. U. S. 

 Nat. Herb. 19:661, 1915). They assign short-pedunculate or sessile heads subtended by 



