RYDBERG: PHy APHICAL NOTES 465 
Northern 
Douglasia nivalis Antennaria sedoides 
Phacelia Lyallii Macronema Lyallu 
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, 
which 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. Hulsea 
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 Machaeranthera Pattersoni 
Ribes montigenum Pseudopteryxia anisata 
Pentstemon Hallii Senecio invenustus 
Pentstemon Harbourii 
