PLANT SUCCESSIONS OF MT. ROBSON 223 



bardment has diminished, because of gradual decrease of slope 

 and resistance offered by the vegetation. Here birches are at 

 the top of the vegetated area, where the brunt of the bombard- 

 ment must be borne. Below is an area of mature climax forest, 

 which unfortunately has been partly burned. The trail to 

 Robson Pass crosses this cone and affords an excellent oppor- 

 tunity for observation. 



Below the cliffs at Emperor Falls, well within the lower Umits 

 of the Subalpine Zone, is a fine piece of climax forest developed 

 upon talus. Picea Engehnanni is dominant among the mature 

 trees. Abies lasiocarpa is less common in mature condition, 

 but in young growth is very abundant. Layered masses of it 

 are so dense as to be penetrated with difficulty. The her- 

 baceous growth is similar in character to that of the area near 

 Lake Kinney. Fatsia is absent however. 



3. The Moraine Succession 



The series of moraines bounding the forefront of the Robson 

 Glacier presents unusual opportunities for study, not the least 

 important being that the usual camp ground is but five minutes 

 walk distant. The Robson Glacier, approximately five miles 

 long, pushes its lower end to the summit of Robson Pass, the 

 altitude of which is 5550 feet (1708 meters). Its front is a little 

 more than half a mile (approximately 1 km.) in extent. The 

 zone of recent moraines that bounds its front is in most places 

 about a quarter of a mile wide, and the recessional ridges are 

 five in number, including that upon which the edge of the ice now 

 rests. At one point near the northeast end of the front there is a 

 projecting knob of rock just beyond the ice edge, and the series 

 of moraines, much compressed, passes over its summit, widening 

 upon each side. The ice did not entirely override this knob in 

 its recent advance. Upon its leeward slope there is a small 

 but exceedingly luxuriant patch of climax forest, in which the 

 ground is deeply covered by mosses. Layered Abies lasiocarpa 

 is very abundant here. The contrast between this and the im- 

 mature climax forest upon the recent moraines is very striking. 



