Rydberg: Phytogeographical notes 465 



Northern 



Douglasia nivalis Antennaria sedoides 



Phacelia Lyallii Macronema Lyallii 



2. Alpine rock-slides 



Many parts of the Rocky Mountains are covered by loose 

 rocks, often in more or less unstable conditions, sometimes forming 

 sliding fields or moving together with the snow avalanches. These 

 are not wholly without vegetation and there are certain plants 

 that are characteristic of such rock-slides, scarcely growing any- 

 where else. 



The most characteristic plant of the rock-slides is, perhaps, 

 Claytonia megarrhiza with its large red root lodged far down among 

 the rocks. Another is Alsine americana of the northern Rockies, 

 w^hich has a slender rootstock, sending up long shoots among the 

 rocks, the proper leaves and flowers crowded at the ends of the 

 branches. Senecio carthamoides and C. Fremontii, Telesonix 

 Jamesii and T. heucheriforme, Ribes montigenum and R. parvulum 

 are also confined to the rock-slides, the former of each pair found 

 in the southern, the latter in the northern Rockies. Hidsea 

 carnosa also I found only in the rock-slides of Montana and Yellow- 

 stone Park. Primula Parryi and Oxyria digyna frequent the 

 rock-slides, but are not confined to them, the former being 

 even found in the woods. The other rock-slide plants are rather 

 local. 



The following constitute for the most part the rock-slide 

 vegetation : 



Southern Rockies 



Polemonium speciosum Aquilegia saximontana 



Polemonium confertum Syntheris plantaginea 



Primula Parryi Senecio carthamoides 



Claytonia megarrhiza Oxyria digyna 



Telesonix Jamesii Selaginella densa 



Heuchera Hallii Machaer anther a Pattersoni 



Ribes montigenum Pseud opteryxia anisata 



Pentstemon Hallii Senecio invenustus 

 Pentstemon Harbourii 



