226 GENUS CHRYSOTHAMNUS. 



Within the typicus group it is found that subspecies speciosus probably includes the 

 plexus from which the others have arisen. As originally described, this is a rather low, 

 narrow-leaved, gray plant with close, rounded inflorescences. This form is common in 

 the basin of the Columbia River, extending south through eastern Oregon and east into 

 Idaho, etc. Farther southward and southeastward it passes gradually into a more robust 

 form with wider leaves (minor variation 58) , while to the east it becomes taller, but with 

 only a slight widening of the leaves. In the Rocky Mountain States it is commonly a 

 tall, tree-like shrub with large, open inflorescences, the involucres more nearly glabrous, 

 and the leaves slightly wider than in the tjT)ical form. This most easterly variation 

 has been described as C. pulcherrimus Nelson (minor variation 68). It comes very close 

 to connecting speciosus directly with graveolens. Thus, speciosus as here conceived includes 

 a number of minor variations, which can be correlated roughly with geographic distribu- 

 tion, but none of which are sufficiently well marked to be given definite taxonomic status. 

 In addition to these there are five stronger groups, each of which is given subspecific rank. 



The subspecies latisquameus, a tall shrub of Arizona and New Mexico, is perhaps more 

 distinct from speciosus than any of the others just mentioned. It is, however, given a 

 position close to speciosus, because of its possible connection with a preceding subspecies, 

 namely, hololeucus. In common with this latter it has a loose, white tomentum, excep- 

 tionally obtuse involucral bracts, short corolla-lobes, and a tendency toward an arach- 

 noid pubescence on the corolla-tube (see minor variation 8). However, because of the 

 proportionately longer style-appendages, it is provisionally referred to the speciosus group. 



The subspecies albicaulis is perhaps the least distinct from speciosus of any included 

 in this circle, having only its floccose and very white tomentum as a constant character. 

 However, this difference holds without exception, there being no intermediates, even 

 when the two grow side by side. The nature of this character difference has been dis- 

 cussed on page 170. Typical albicaulis grows with typical speciosus in the Columbia 

 River Basin, while to the south it becomes more robust and the leaves are wider (minor 

 variation 25), thus paralleling a similar variation found in southern plants of speciosus. 

 This subspecies extends east only to western Montana and Utah. It is looked upon as a 

 probable mutation from the western form of speciosus. 



The subspecies typicus is now definitely restricted to certain low shrubs of the plateaus 

 of the northern Rocky Mountain States. It has been frequently assumed that typical 

 C. nauseosus was the northwestern plant here called subspecies albicaulis. The error of 

 this application of the name is discussed under minor variation 20, where the identity of 

 the original Chrysocoma nauseosa with the plant often known as Chrysothamnus frigidus 

 is pointed out. Subspecies typicus is looked upon as an easterly derivative of speciosus 

 which has undergone a reduction in the size of the heads and flowers and which has 

 assumed certain vegetative characters that enable it to persist under the unfavorable 

 conditions of its cold, bleak, and sometimes alkaline habitat. Its most important minor 

 variations probably are ecads, since they are recognizable only by the size and direction 

 of the leaves (minor variation 35, C. frigidus, and minor variation 67, C. plattensis). 



The subspecies salicifolius is but little known, but seems to have split off from subspe- 

 cies speciosiis along the southeastern limits of the range of this latter. It is a robust plant 

 with exceptionally wide, 3-nerved leaves. 



The most unique feature in the speciosus group has been developed in the subspecies 

 occidentalis. This is the abrupt narrowing of the tips to the involucral bracts. The 

 narrowing is least noticeable in plants of northern California, where the two subspecies 

 are in contact, but it becomes more and more pronounced toward the south. The 

 bracts are only slightly puberulent or sometimes practically glabrous and the heads are 

 in small, compact, globoid cymes. The following note on occidentalis is from a recent 

 paper by Hall (Univ. Calif. Publ. Bot. 7:168, 1919). 



