TORREYA 



September, igio 

 Vol. lo No. 9 ^^^^^^ic^ 



POTENTILLAE OF THE ARCTIC-ALPINE ZONE ^^*^ 



ON PIKE'S PEAK 



Five species of Potentilla, with their near relative Dasiphora 

 fructicosa, appear within this zone on Pike's Peak. 



P. saximontana Rydb. is by far the most abundant and con- 

 spicuous. It occurs everywhere and exhibits many variations 

 of habit due to its environment. Ordinarily of a caespitose habit, 

 in well-watered situations it becomes more branching and erect; 

 in dry wind-swept areas a plant often consists of a single pros- 

 trate caudex. It blooms through the entire growing season and 

 may be found even late in October in protected spots. Dr. 

 Rydberg said of the specimen I submitted to him for identifica- 

 tion: "P. saximontana Rydh. approaching rubripes; I am afraid 

 the two species run too much into each other and probably are 

 but one." The other species of the group "Rubricaules" of the 

 Flora of Colorado which have been reported from Pike's Peak 

 evidently were the variations of this species. 



P. viridior Rydb. is often similar to P. saximontana in habit 

 but differs in its narrower, darker petals and larger leaf surface. 

 It blooms earlier in the same localities and typical plants are 

 taller and "stemier" with the leaves darker green above. Ac- 

 cording to Dr. Rydberg the leaves of the plants of this locality 

 seem to be whiter beneath than those of the type plant. This 

 species is quite frequent along trails and rivulets up to 12,200 

 feet. 



P. filipes Rydb. is quite variable and not found above 12,000 

 feet. This species is P. pulcherrima of the Flora of Colorado 

 but the altitudinal range should be extended upward 2,000 feet, 

 for it occurs in dense patches on grassy banks well above timber 



[No. 8, Vol. 10, of ToRREYA, Comprising pages 169-192, was issued August 29, 

 1910.] 



193 



