266 THE JOURNAL OF BOTANY 



scarce and dwarfed ; it was only observed in two sheltered places, 

 in one of which there were but few plants, in the other it was 

 locally abundant. Many other common plants were only noted 

 in small quantity in one place, such as Heracleum Sphondylium 

 and Tussilago Farfara, some in two places, and these were 

 evidently introductions. One undoubted introduction, Matricaria 

 suaveolens, was abundant near the landing-place at Baltasound ; 

 this is rapidly spreading in the manufacturing districts of York- 

 shire, especially in sandy soils. 



The number of vascular plants marked off in a catalogue on 

 the spot during August was 238, consisting of 221 species, 

 4 varieties, and 8 bracketed as certainly planted. Not counting 

 the 8 last mentioned, 51 of these species and 1 variety were seen 

 only in Unst, 37 species and 1 variety only on Mainland, and 

 133 species and 2 varieties in both Unst and Mainland; 9 of 

 those seen on Mainland were only noticed between Lerwick and 

 Scalloway. This shows that 187 of these were noted for Unst 

 and 173 for Mainland. 



The truly vernal plants had mostly vanished. The presence of 

 alpine and even Arctic plants at 50 to 100 ft. above sea-level is a 

 marked feature, such as Silene acatdis, Arabis petrcea, the nigre- 

 scent form of Cerastium arcticum, Thalictrum aljjinum, Draha 

 incana, &c. Edaphic influences were very marked, some plants 

 being abundant on, and others confined to, the Serpentine. For 

 instance, Selaginella selaginoides was strikingly abundant on this 

 formation everywhere, so much so, that in some places the dis- 

 tance of the tufts from each other varied from 3 to 6 in., in others 

 from 9 to 12 in. Statice Armeria (not seen at all near Ollaberry) 

 and Thalictrum alpimcm were quite absent on all the granite I 

 visited, even at an elevation of 1470 ft., but at low elevations they 

 were both common on the Serpentine. Even Linum catharticum 

 was not noticed about Ollaberry either on the schist or the granite. 

 Other plants, such as Gyrophora torrefacta, Platysma triste, 

 Parmelia lanata, Hedtoigia ciliata, and others, were all confined 

 to the granite. The very rare Arenaria norvegica, Cerastium 

 arcticum, a peculiar rigid and nigrescent form of C. vulgatum, 

 Plantago maritima v. lanata, and others, were also restricted to 

 the Serpentine. 



Another feature was the abundance of certain plants in some 

 districts and their total absence in others ; as an example, Gen- 

 tiana campestris was in great profusion in Unst and quite absent 

 from the district about Ollaberry in the north of the Mainland. 

 There is a very marked influence of cold winds — in the more 

 exposed places — on the stature and state of plants ; all the Festuca 

 ovina was viviparous, even at about 120 to 140 ft. above sea-level. 

 Molinia coerulea was about 6 in. high but often less ; Bhinantlius 

 Crista-galli and Linum catharticum were often unifloral and but 

 2 to 3 in. high ; Carex flava varied from 1 to 2 in. in length ; 

 Scabiosa succisa stood about 3 in. ; there were plenty of dwarf 

 plants of Lotus corniculatus with but one fruit, and many tiny 

 plants of Prunella vulgaris with often only one verticillaster. 



