190 Viiiiu rsilji of Califoriiid /'t(h1icatio)is in lU/hnnj | \'<m.. 7 



found ill tell of its species and in ralluT ]i\rgo amounts in two of these, 

 vol the iiijiii-])ereenta<»'e species are small ]>Iants. This <i-enns will he 

 dealt with elsewiiere.'' 



The otln'i', tliat is, Cliri/solliarnints, is a West American genus of 

 about sixteen iiiajor species, but these ineluch' so many variations that 

 sonic botanists would recognize nioic than one hundred specific segre- 

 gates. Eleven of the major si)ecies of Clirysolhainiius have now been 

 examined and rubber found in tive of them. One of these, C. nausrosus, 

 is of outstanding promise; the othei- four are discussed further on.'' 



Botanists are far from agreement as to the limitation of species in 

 the genus, but for pi-actical purposes it seems best to adopt a broad 

 species concejit and to recognize a considerabh^ number of varieties 

 under each of the sj)eeies. According to this ai-rangement Chrijso- 

 tlidiiuuis )i(iHseosus constitutes a nuijor species with twenty-two 

 varieties. Twelve of these have been examined for rubber and it was 

 found to be present in all of them. The complete botanical designa- 

 tion of each variety may be expressed by a trinomial, for example, 

 Chrysothammis nanscdsns var. gravcolciis; ('ItrysotlianiiiKs nauseosns 

 var. viriduhis, etc., but for simplicity we may be permitted, in a special 

 paper such as the present one, to omit the generic and specific names 

 and refer to the various forms only by their varietal names. We shall, 

 therefore, use such detached terms as graveolms and viridulus to ex- 

 press our concept of the respective varieties belonging to the very com- 

 plex species known as ('hr^isofhoiinnis nanseosus. It is ho])ed that this 

 simplification will appeal to the non-botanical reader, who often has 

 little time for and less interest in an involved taxonomic terminology 

 and that it will, at the same time, meet the needs of the professional 

 botanist. In some cases the name of a species itself will be used in- 

 dependently of its generic name. The exact taxonomic position of any 

 variety of (y'krysotlium)nis nauseosits may be determined by reference 

 to pages 15<) to 181. 



The correct common name of ('IirysotJianDius, and more particu- 

 larly of C. nauseosns, and its varieties is Rabbit-brush, a name which 

 has been in use both among non-botanists and in botanical litiM-ature 

 for at least twenty-five years. Through erroneous identification it has 

 been frequently ap])lied to other plants. In two ])uhlieations it has 

 been used indiscriminately" for species of Chrijsotli'iiiuitis, T( I nid i/miii. 



•■•' See pp. 268-274, 

 « See pp. 265-268. 

 7 X. Am. Fauna, no. 3.") (1913), pp. 28, 31. 37; no. 42 (1917), pp. 79. 81. 



