C. PYRAMID ATUS. 197 



teristic appearance, for the flowers project beyond the involucre a distance equal to one- 

 half their own length, the pappus thus appearing like an elongated brush. 



In describing depressus, Nuttall stated that it was close to pumilus, that is to C. 

 viscidiflorus pumilus of this monograph. While it is probably closer to viscidiflorus than 

 to any other species outside of its own section, its connection is more likely to be through 

 some subspecies of the pubescent-stemmed series and probably through one discovered 

 since Nuttall's time. It is almost matched in habit by subspecies humilis, but the geo- 

 graphic isolation of this form is against it as a close relative of depressus. About all that 

 can be said, therefore, is that pulchellus and depressus are intimately associated phylo- 

 genetically and that this branch is probably a derivative of, or has given rise to the 

 viscidiflorus group of subspecies, presumably through some form close to humilis. 



ECOLOGY AND USES. 



Chrysothamnus depressus grows sparsely as a subclimax undershrub on rocky slopes, 

 or in pockets of soil on cliffs. It also persists into the climax stage, where it occurs with 

 Bouteloua gracilis. 



This species is usually found to be closely cropped, apparently by sheep, but it is not 

 sufficiently abundant to be of much importance as browse. 



Section IV. NAUSEOSI. 

 10. CHRYSOTHAMNUS PYRAMIDATUS (Robinson and Greenman). Plate 30. 



Shrub 6 to 9 dm. high, the branches probably ascending; ultimate twigs widely spread- 

 ing, sparsely leafy, covered with a close white tomentum, this deciduous in the second 

 year, the bark then brown; leaves more or less fascicled, narrowly linear, with closely 

 revolute margins, cuspidate, 0.5 to 3 cm. long, about 0.5 mm. wide, 1- or 2-nerved, 

 green and viscidulous abovei obscurely tomentulose to white-woolly beneath ; heads 

 numerous, in dense leafy-bracted lateral spikes which are assembled into terminal 

 pyramidal panicles; involucre 6 to 7 mm. high; bracts about 15, the ranks obscure, 

 1-nerved, lanceolate, the margins hyaline, loosely puberulent, none with herbaceous tips; 

 flowers 5 to 10; corolla tubular-funnelform, 4 to 5 mm. long, the tube glabrous; lobes 

 about 1 mm. long, lanceolate, recurved, puberulent at tip ; anther-tips lanceolate, acute, 

 about 0.3 mm. long; style-branches long-exserted, thick, barely acute, the appendage 

 about as long as the stigmatic portion (but material young and not satisfactory) ; achenes 

 appressed-villous ; pappus about equaling the corolla, soft, sordid or tawny. (Bigelovia 

 pyramidaia Robinson and Greenman, Proc. Am. Acad. 32:43, 1896.) 



Mexico; known only from four collections, all in the States of Oaxaca and Coahuila. 

 Type locality, on the hills above Oaxaca, altitude 1,700 m. Collections: Type collection, 

 November 16, 1894, Pringle 6048 (Gr, UC, US); Canada Sta. Maria, Oaxaca, Seler 1477 

 (Gr); Monte Alban, near Oaxaca City, Oaxaca, between 1,700 and 1,850 m. altitude, 

 Smith 371 (US) ; Sierras de Parras, Coahuila, in rocky soil, Purpus 1326 (UC, involucral 

 bracts scarcely acute). 



RELATIONSHIPS. 



The exact position of C. pyramidatus in the genus is not certain, but it is placed in 

 the Natiseosi because of the pannose tomentum of the twigs. The decidedly spicate or 

 subracemose inflorescence is suggestive of a remote relationship with C. parryi. How- 

 ever, there is no tendency toward an attenuation of the tips of the involucral bracts 

 and the style-tips are much less acute than in parryi. The villous-puberulent corolla- 

 lobes occur elsewhere in Chrysothamnus only in C. parryi latior and in a few of the less 

 specialized subspecies of C. nauseosus. The present species possibly represents a primi- 

 tive type or oif shoot from the main line, as its Mexican habitat also suggests. 



