PLAISTT 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 [A^mhis drummondu) , 



(Vagnera sfe/ZaZ-ay 

 Fig. 13. — Plants characteristic of the early second-weed stage. 



low larkspur {Del'pMnmmh, men^iesii), scarlet gilia, {Gilia pul- 

 ckella), peppergrass (Lepldium rmnosisslmum) , bladder pod {Les- 

 querella utahe'nm)^ plantain {Plantago tweedy i), and butterweed 

 {Senecio columbianus and S. crassulus). 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 

 f eedei*s. Generally the roots are rather shallow, the moisture supply 

 being procured chiefly from the upper foot of soil (figs. 15 and 16). 



