352 Vni. ALTITUDE OF SPECIES. 



of science. It will thus happen, that much time is lost in noting and 

 calculating the heights for the same plants again and again, through 

 successively finding them higher and higher, or (in case of the alpines) 

 lower and lower, than the spots at which their altitudes had been before 

 noted and calculated. Much of that troublesome repetition may now be 

 avoided ; because heights decidedly within those stated in the lists may 

 now be disregarded unless under special circumstances; those about 

 (above or below) the indicated limits being more especially and almost 

 exclusively such as still require to be carefully noted. Pioneers are 

 compelled to advance slowly and laboriously. A way once made, and 

 landmarks fixed, their successors can get on more quickly ; accom- 

 plishing more, and in less time. 



V. LOWER LIMITS OF SPECIES. 



Saxifraga cernua, 2.1Q cent. Perthshire, down to 1250 yards. 



Saxifraga csespitosa, 2.20 cent. Aberdeenshire, say at 1200 yards. 



Carex lagopina (leporina), 2.25 cent. Aberdeenshire, rather lower. 



Luzula arcuata, 2.80 cent. Sutherland, say at 1000 yards. 



Poa laxa, 3.20 cent. Grampians, at 1000 yards, less or more. 



Poa minor, 3.20 cent. The same, and also uncertain. 



Ce.astium latifolium, 3.20 cent. Grampians, at 1000 yards. Lower? 



Draba rupestris, 3.25 cent. Sutherland, say at 900 yards. 



Stellaria cerastoides, 3.50 cent. Ben Nevis, at 900 yards, near snow. 



Saxifraga rivularis, 3.50 cent. The same, also irrigated from snow. 



Juncus biglumis, 3.70 cent. Grampians, at 900 yards. Seldom so low. 



Aira alpina, 3.70 cent. The same. Altitude ill ascertained. 



Cystopteris montana, 3.70 cent. Grampians, say at 900 yards. 



Menziesia caerulea, 3.70 cent. Perth, about 900 yards. Single locality. 



Carex saxatilis, 4 cent. Easterness, rather below 850 yards. 



Carex aquatilis, 4 cent. Forfar, 850 yards. Different species lower? 



Salix reticulata, 4 cent. Bocks in Perth and Forfar, at 850 yards. 



Erigeron alpinus, 4 cent. The same. 



Carex atrala, 4 cent. The same. 



Areuaria rubella, 4.10 cent. Perth, at 850 or 830 yards. 



Cherleria sedoides, 4.10 cent. The same. If in Shetland, r.t 450. 



Salix procumbens, 4.20 cent. Grampians, at 800 yards ? 



Salix Myrsinites, 4.20 cent. The same. Forfarshire, etc. 



Gnaphalium norvegicum, 4.20 cent. The same. 



Gentiana nivalis, 4.20 cent. The same. Among rocks. 



