248 Scottish Mountain Platits. [Sess. 



dition near and at the tops of our highest mountains.'^ Even 

 plants that are confined in Scotland to the higher parts of 

 mountains show very considerable variation in size, as may 

 be seen by comparing the plants of Saxifraga stellaris, &c., 

 at the summits of the Breadalbane Mountains with the 

 examples that occur, say, a thousand feet below. 



Shrubby plants, when they occur, are likewise compact and 

 bushy, owing to their branches being numerous and short. 



Xerophilous Features. — The general stunted character of 

 mountain plants is due to the nature of their environment. 

 The stormy winds, the sudden extremes of temperature, and 

 the rarefaction of the mountain air, all tend to favour a dwarf 

 growth. Many of these plants have to undergo a period of 

 drought, — drought not produced so much by heat as by 

 winter cold and the desiccating eft'ects of winds. To prevent 

 death taking place from loss of water, many mountain plants 

 are found with adaptations which check transpiration. Thus 

 the leaves may be stiff and leathery, with a reduced surface 

 (Lycopodium), succulent or fleshy (Saxifraga oppositifolia, 

 Sedum roseum), with stomata partially concealed (Empetrum), 

 hairy on the under surface (Dryas, Plate XXIV., Fig. 1), waxed 

 on the under side (Vaccinium Vitis - Idsea, Salix reticulata), 

 densely covered with hairs (Antennaria, Salix Lapponum, 

 S. lanata), rolled up and strongly cuticularised (Grasses and 

 Sedges, as Festuca ovina, Nardus, Carex rupestris, &c.).' 

 Loiseleuria (Plate XXIII.) has rigid leaves with revolute 

 margins, and downy beneath. 



Plate XXI. shows the half-exposed mountain rocks during 

 spring, when the plants are most liable to suffer owing to 

 insufficient moisture ; for it is when oft-repeated winds and 

 sunshine accompanied by frost occur that desiccation is liable 

 to take place, owing to the loss of water from the shoots — 

 water which, if lost, cannot be replaced, owing to the roots 

 being frozen in.^ At one time it was supposed that the 



1 The Dandelion was one of the plants that the late Mr Ball found in flower 

 on the Aletsch Glacier, 10,700 feet above sea-level. 



^ See Schimper's Plant Geography, p. 679. 



^ Many plants, upland and lowland, which do not die below-ground in autumn, 

 are liable to this danger, especially in spring when the air is warm and in rapid 

 motion, while the soil is frozen. The injury done is usually, but erroneously, put 

 down to the direct action of frost. 



