270 THE JOURNAL OF BOTANY 



Leciclea hardly determinable), Physcia aqiiila, P. jxtrietina, 

 Collema sp. (on the soil in crevices), Ulota phyllantha and Homa- 

 lothecium sericeum. Lichens and Muscinege ^Yere anything but 

 plentiful on the rocks of this formation on account of its rapid 

 weathering. 



An extensive part of the moorland in the west of Unst was 

 very carefully examined with regard to the relative proportion of 

 species. The land was at an elevation of between 200 and 300 ft., 

 in some parts it was flattish, the rest gently sloped to the Atlantic. 

 The approximate percentage numbers of the species were : Bhaco- 

 mitrium lanuginosum [= Grimmia hypnoides] (60), Calluna (20), 

 Eriophorum polystachion (10), Emioetrum nigrum (4), Erica 

 cinerea (2), E. Tetralix (2—), Narthecium (2 + ); Drosera rotundi- 

 folia was very scarce. Cladina sylvatica was sprinkled amongst 

 the Bhacomitrmm, and now and then increased into patches. 

 Cladina iincialis occurred here and there, and forms of Cladonia 

 furcata. Sidkagmim acutifolium occasionally was present in small 

 quantity, and S. cuspidatum in hollow places. Small patches of 

 Campylopus brevipilus was on the bare soil now and then. Rocks 

 abutted irregularly, and about these was Spli(Erophorus coralloides, 

 and on them grew a great abundance of Parmelia sulcata, with a 

 very much smaller proportion of P. physodes, and here and there 

 various forms of Lecidea contigua. 



As the relative proportion of the floral constituents often 

 changes very rapidly on the same geological formation, I made a 

 careful examination at a fair distance from the last place, at about 

 the same elevation and with about the same aspect ; there was 

 nothing on the surface to indicate any difference in soil, the only 

 difference was that it was all a gentle slope without small flattish 

 areas. The Rhacomitrium had practically disappeared. The con- 

 stituents were approximately as follows : — Agrostis tenuis (18), 

 Calluna (12), Festuca ovina — mostly viviparous (12), Aira flexuosa 

 (7), Juncus squarrosus (6), Luzida congesta (6), L. sylvatica (3), 

 Potentilla sylvestris (3), Hylocomium loreum {4:),Polytrichum com- 

 mune (4), P. juniperinum (3), Hypnum cupressiforme (3), Tliuidium 

 tamariscinum (2), Cladonia — several species (2), the rest, bareness 

 (15). This shows — as I have often noticed — how difficult it is to 

 colour a phytogeographical map correctly in every district except 

 on a very large scale. 



The flattish top of another moorland south of Baltasound, 

 three or four miles from the last moor, was examined, and found 

 to be occupied with the following : — Rhacomitrium lanuginosum 

 (70), Calluna (20), Erica cinerea (4), and a mixed formation (6) of 

 Festuca ovina — viviparous, Plantago maritima, Potentilla sylves- 

 tris, EmjMrum, Agrostis tenuis, with odd plants here and there of 

 Carex sp. (cropped, probably hinervis), C. pilulifera. Thymus 

 Serpyllum, Viola canina (badly attacked by Puccinia Viola), and 

 the large flowered form of Aira flexuosa. As one proceeded down 

 the slope the Rhacomitrium diminished (60), so did the Calluna 

 (15), the Erica cinerea increased (15), the rest (10) consisted of 

 those plants under " (6)" — a few lines above — with the addition of 



