AN fECOLOfJICAL PROBLEM. 229 



more closely at the floras of the different mountains of the range. 

 On the rocks overlooking Lochan a' Chait, on Ben Lawers, we 

 have the following very rare plants : — Cochlearia groanlandica, 

 Saxifraga rivularin, S. caespitosa, Myosotis alpestris, Salix 

 reticulata, Jujtcus bighimis, Phleu7n alpinum, Woodsia hyperborea, 

 and Cystopteris montana ; on the rocks of Meall Garbh, also over- 

 looking Lochan a' Chait, we find these plants more numerous and to 

 all appearance growing more luxuriantly, with the exception of 

 Saxifraga rivularis, which, however, it must be admitted, does 

 not seem at home on Ben Lawers — but then we have Erophila 

 injiata, Erigeron alpinum, Gentiana nivalis, and Kobresia caricina 

 in addition, and here we find also that form named Cerastiuvn 

 trigynum by the older botanists, and which has a very close 

 resemblance to that plant. Then if we take the western side of 

 Ben Lawers. we find at the head of the ravine a marked change 

 in the general appearance of the flora at the same elevation. 

 Here, we see, is the habitat proper of Myosotis alpestris and 

 Gentiana nivalis. Looking more closely, we find Arenaria sulcata 

 and Sagina nivalis, and although we miss nearly all the plants 

 mentioned on the eastern side, to make up for this, as it were, we 

 have all the rare cryptogams. Now, if we ascend the southern 

 slope towards the Ordnance Ravine, we find Loiseleuria 

 procumbens, a plant not found elsewhere on the mountain now, 

 and in the ravine we come aci'oss Draba rupestris, the fast dying- 

 out Saxifraga cernua, and a number of the rai-er cryptogams, all 

 upon the rocks having a western exposure, while the rocks of 

 Beinn Ghlas on the other side of the western ravine, and likewise 

 having a western exposure, are almost barren of alpine plants, 

 none of those we have mentioned being found on them. 



Coire Liath, Meall Corranaich, and Coire Odhai", all over 3,000 

 feet, and of the same rock formation, we pass as almost destitute 

 of rare species, and take up Creag-an-Lochain, where we again 

 meet with many of our rai'e forms, even at much lower levels than 

 on Ben Lawers. Woodsia hyperborea is still to be found growing 

 with Geranium lucidum under 2,000 feet, and more luxuriantly 

 than on Ben Lawers. Among others, Erojjhila infiata, Cochlearia 

 groenlandica, Sagina nivalis, Juncus bighimis, and Phleuin 

 alpinum occur, and now this point is the eastern limit of Dryas 

 octopetala and Juncus castaneus. Meal nan Tarmachan is 



