The Scottish Naturalist. 293 



nosis its proper place or even significance \ nor can we afford to 

 overlook or even neglect any, provided the results by it are 

 definite: and such is true of chemical tests. The reactions by 

 K and C as regards Usnea are sharply defined so far as they 

 go ; and the same is true of I, although its reactions are occa- 

 sionally somewhat troublesome to develop, owing, probably, to 

 the gelatine being contained in cell-walls not easily permeable 

 by the solution employed. A little friction is generally quite 

 sufficient to develop the characteristic colour ; and in doubtful 

 cases this should always be had recourse to before desisting 

 from its application. 



At this stage some alterations and modifications of parts of 

 the first paper are necessary. 



The Usnea alluded to at p. 107 of previous paper has pecu- 

 liarities of constitution sufficient to entitle it to rank as a species. 



Usnea fragilis sp. now — Thallus lutescenti-pallidus, robustussed 

 fragilis, erectus vel prostratus, divaricato-ramosus, supra 

 densius ramulosus, fere fibrillosus, minute sed creberriter 

 sorediosus ; axis crassiusculus ; fibrillar medullares com- 

 pacts, interiores pallide citrinos, exteriores purpurascenti- 

 rubentes, I — •, K fl. C aurantiacae. 



Ad arbores in Montibus Nilgherrensibus Indiae Or., a D re G. 



Watt lecta. 

 K causes the purplish-red colour of the medulla to disappear. 



In U lliomsoni of same paper, the axis is slender and the 

 medullary fibres arachnoid ; while in specimens collected by Dr 

 G. Watt from the same range of mountains, the blackened tips 

 of the ramules are, at times, scarcely perceptible. 



Under U. sublurida lurk several species from various parts of 

 the world, notably from South Africa and Australia. This group 

 may be characterised by having red splatches pretty generally 

 scattered over the surface of the stems and branches, while the 

 external reactions of thallus, K — or faint yellow C yellow, are 

 common to all. In Scottish specimens, the stems and main 

 branches are nearly uniformly red, as stated in the diagnosis of 

 U. sublurida, but the red patches are interrupted upwards, and, 

 to this extent, the diagnosis requires modification. 



Usnea maculata sp. nov. — Thallus rigidus erectus, varie ramosus 

 sed plerumque fibrilloso-strigosus (ut in U. hirta), interdum 



