GENERAL CHARACTERISTICS 23 
filled with rich vegetable mould mixed with flakes and 
particles of stone, and in these fertile beds, often of vast 
extent, we find a wondrous variety of plants. A large 
proportion of the fleshy or tuberous rooted plants will be 
included in these groups, and it is also to be noted that 
whereas the prominent and exposed rocks are clothed with 
prostrate and clinging plants, the hollows and stretches 
of which we are now taking note give us plants of erect 
and sometimes tall growth. This is explainable by two 
reasons. First, the shelter afforded by the surrounding 
rocks enables plants to grow which would, in more ex- 
posed positions, be torn and broken by winds; secondly, 
with the depth of rich soil available the surface of the soil 
becomes carpeted with an intermingled and tangled mass 
of grass and weeds, and it is only those plants that can 
push their way through this reeking tangle of rank growth 
and rear their heads in the free daylight and air that can 
survive. Wwo useful hints are thus conveyed to us, one 
being that in planting we should provide the taller grow- 
ing Alpines with the warmer and more sheltered positions, 
the second that often a plant with thick, fleshy roots requires 
either deep planting or something in the way of a carpeting 
plant that will keep the soil cool in summer and com- 
paratively snug and warm in winter. 
I need not delve deeply into science to explain how 
alternate freezings and thawings with consequent expan- 
sion and contraction causes considerable portions of the 
face of apparently hard rock to become disintegrated and 
crumble away. When after the snow and frost-bound 
winter the sun thaws the snow and ice, causing avalanche 
