238 WILLIAM S. COOPER 



The Moraine Succession, as seen upon the five recent moraines 

 of the Robson Glacier, comprises three telescoped stages, having 

 their beginnings at the same time, representatives of all three 

 being present upon the moraine most recently deposited. The 

 stages attain dominance in successive order. The first com- 

 munity to become recognizable is characterized by the ground- 

 shrubs Dry as octopetala and Arctostaphylos rubra. This is 

 followed by a tall shrub stage including several species of Salix 

 and Betula glandulosa. The third stage is the climax forest of 

 Picea, Abies, and Pinus albicaulis, which has not yet attained 

 its full development upon these deposits. The spaces between 

 the climax trees are still occupied in part by the Salix-Betula, 

 Community, in part by the Dry as- Arctostaphylos Community. 



The Shingle Flat Succession has its normal beginning upon wet 

 stream-borne deposits. The pioneers differ according to the 

 size of the soil materials. If they are coarse, Epilobium lati- 

 folium and Saxifraga aizoides, both annuals, are the characteristic 

 first arrivals; if fine, perennials of the sedge and rush types 

 are the pioneers. In either case, moisture conditions remaining 

 good, a willow thicket follows these, and is itself followed by the 

 climax forest. If the flat becomes desiccated through down- 

 cutting by the streams flowing over it, a set of relatively xero- 

 phytic pioneers replaces the wet shingle species, the most impor- 

 tant being Dryas Drummondii. In such a case the willow thicket 

 is omitted, and a relatively xerophytic subclimax forest stage 

 is inserted, composed in the Lake Kinney locality of Pinus 

 Murrayana and Betula papyrifera in addition to the climax 

 conifers. On the dry shingle flat upon Robson Pass the stages 

 are almost identical with those of the succession upon the Rob- 

 son moraines. The progress of the succession upon the moraine 

 has been much the more rapid, in part at least because the water 

 retaining capacity of the soil is greater, the particles being much 

 finer. 



