VALUE OF HAIBS AS A SPECIFIC GBOUP-CHARACTEB. 17 



On the value of Hairs, as a Character in determining the Limits 

 of subordinate Groups of Species, considered in connexion 

 with the Genera Eurybia (Cass.) and Olearia (Monch), of 

 Coinpositae. By William Archer, Esq., F.L.S. 



[Read March 1, I860.] 



My attention was first directed to the question of the value of 

 hairs, in determining the differences between closely allied species, 

 by a passage in one of Dr. Lindley's admirable botanical works, 

 ' The Introduction to Botany ; ' and I have constantly made use 

 of this character, often finding it of practical application, espe- 

 cially in separating dried specimens. For example, the distinc- 

 tion between Cassinia aculeata (Br.) and Ozothamnus rosmarini- 

 folius (Br.) cannot otherwise be ascertained without an examina- 

 tion of the receptacles of the specimens ; but they may be quickly 

 separated by means of the hairs, those on the stem of the former 

 plant being tomentose, while those on that of the latter are 

 arachnoid. 



Having perceived that much discussion had taken place as to 

 the generic difference between Eurybia (Cass.) and Olearia 

 (Monch), I examined the species of both genera within my reach 

 in Tasmania. The result was, that the hairs on the leaves of the 

 (then) reputed Olearice (O. lirata, fulvida, and Ounniana) proved 

 to be stellate, while those on the leaves of the reputed Eurybia 

 (E. argophylla, viscosa, alpina, &c.) were T-formed. I afterwards 

 found that other species of Eurybia had woolly hairs on the leaves, 

 others glandular, and others, again, septate. 



By the kindness and liberality (so well known and appreciated) 

 of Sir William Hooker, who permitted me to study the whole 

 of the species of Olearia and Eurybia contained in his unrivalled 

 Herbarium, I was enabled to obtain all the information that I con- 

 sidered necessary to solve the difficulty before me. 



However, I soon discovered that, if I were to go thoroughly into 

 the subject, I should speedily be beguiled into Diplopappus and 

 its allies, and should probably soon find myself deep in other 

 genera, the very names of which were as yet unknown to me. 



Therefore I determined to content myself, for the present, with 

 a classification of all the species of Olearia and Eurybia (to the 

 number of fifty-two) of which there were good suites of specimens, 

 according to the form of the hairs on their leaves, and then ascer- 

 tain how far the character derived from the hairs was supported 



LINK. PBOC. — BOTANY, VOL. V. 



