228 THE JOURNAL OP BOTANY 



found that cryptogamic plants are very sensitive to such in- 

 fluences, and often form a reUable index to the cHmatic and 

 geological conditions of the environment. 



But before the effect of these conditions can be adequately 

 gauged, there is much preliminary work of a systematic and 

 floristic nature to be done. These few notes, meagre as 

 they are, may therefore have their value as a small contribution 

 to our knowledge of one of the more inaccessible and less 

 easily worked " formations," viz. the Upper-Arctic Alpine 

 Formation. 



Before going further it may be well to explain what is meant 

 by the term Upper-Arctic Alpine Formation. It consists briefly 

 of the flora of the higher mountain summits in Great Britain. 

 Where the continuous undulating and rising ground begins to be 

 differentiated into individual summits, a change from the pre- 

 vailing moorland and subalpine vegetation becomes noticeable. 

 In addition to the characteristic plants of such habitats, we begin 

 to find examples of Arctic types ; and, to meet conditions of 

 greater exposure, the morphological features of the species 

 become modified in various ways, with which botanists are now 

 familiar. At 2700 ft. and upwards, the Upper-Arctic Alpine 

 Flora predominates. It is divided by Moss (1) into three groups. 

 The first, the Chomovhyte Association of Crags and Carries, does 

 not concern us here, as we did not meet with this class of habitat 

 on the route by which we ascended Ben-y-Gloe. The two 

 remaining divisions are sections of what K. Smith (2) termed the 

 " Alpine plateau " and Warming " Fell-field." One of them, the 

 Moss-Lichen Association, is an open association occurring on 

 fairly level plateaux and scree-slopes, the vegetation being 

 sparsely scattered over ground strewn with gravel, stones and 

 boulders. The other is a closed association, occurring on slopes 

 of usually less broken ground at similar altitudes, known as 

 BJiacomitrium Heath, which at its lower limits, and under 

 certain conditions, passes into various moorland groups. Two 

 other associations are possibly to be separated within the 

 formation — that dominated by Antlielia (3) on wet rocky slopes ; 

 and the Marsupella Association of Macvicar (4), which is partial 

 to slopes facing east and north, and is dominated by hepatics and 

 such plants as Dicranum falcatnm. The two associations des- 

 cribed in this paper are the Moss-Lichen Association and the 

 Bhacomitrium Heath, which are well-marked and distinct on 

 Ben-y-Gloe, although they frequently show transition stages, and 

 become more or less intermingled. Such modifications we have 

 observed on a slope of Braeriach towards Glen Eunach in West 

 Invernesshire, and elsewhere. 



The flowering plants of these associations have been fairly 

 well worked out and recorded, and we do not propose to devote 

 attention to them now. Many of our most interesting Highland 

 plants are included amongst them, such as alpine species of 

 Potentilla, Alchemilla, Vaccinium, Arctostaphylos, Saxifraga, 

 Azalea, Salix, Juncus, Luzula and Carex. The species are, 



