PLANT SUCCESSION AND RANGE MANAGEMENT. 
39 
than the associated species. Low pea vine, because of its profusion 
of long rootstocks (fig. 12), and the rapid rate at which new shoots 
arise vegetatively, forms the densest cover of any of these rather 
temporary species, 
The further exposure and depletion of the soil usually brings forth 
a conspicuous admixture of a number of other short-lived perennial 
species, some of which may predominate for a time. The most 
characteristic of these are mountain rock cress (Arahis drummondu) , 
(Vagnerct ste/fata)' 
Fig. 13. — Plants characteristic of the early second-weed stage. 
low larkspur (Delphinium, menziesii), scarlet gilia, (Gilia pul- 
chella), pepper grass (Lejndimii ramosissimum) , bladder pod (Les- 
querella utahensis), plantain (Plant ago tweedy i), and butterweed 
(Bene do columhiamis and S. crassidus). Very few grasses are as- 
sociated with this cover. Like their immediately superior associates 
successionally considered, the roots of most of these species are 
specialized, or of the tap order, with more or less conspicuous lateral 
feeders. Generally the roots are rather shallow, the moisture supply 
being procured chiefly from the upper foot of soil (figs. 15 and 16). 
