-63- 
where at present saddles cross the range. Gutting will 
continue at the top and face, and filling will continue 
at the bottom until the lines of cut and fill meet. In¬ 
vasion of mesophytio types will principally be from below, 
the summit holding out longest against the final meso- 
X 
phytic forest. Fig. 35 shows a stage approaching such a 
condition. 
(3) Talus slope. 
In general the width of the talus 
slope depends on the height of the escarpment, especially 
where the latter is not broken by large ledges. When the 
face of the cliff is low, the band of talus is comparative 
ly narrow, for here the rock fragments from above do not 
come in sufficient numbers to prevent invasion of the 
forest below. Where the cliff is high, many of the larger 
, *• 
fsagments may roll 200 or 300 m.,* effectively checking the 
growth of the forest beyond this point. The resulting 
area is desolate in appearance ffig.36), very little 
vegetation gaining a foothold except near the top and 
bottom. 
Where the cliff is principally sandstone, the rock 
fragments are smaller and more flattened than where trap 
predominates. In the former case soil apparently collects 
more quickly and vegetation makes a more rapid invasion. 
