84 TOUE IN SCOTLAND. [April, 



son, viz, from March to September inclusive, before a tolerably- 

 exact estimate of its vegetation can be formed. Ben Lawers 

 would be rather a formidable ascent in the month of March, 

 when in most seasons it is invested in its robe of spotless snow. 

 But doubtless the enterprising muscologist would then find se- 

 veral rarities to repay him for his toil and suffering. 



The beginning of August would however be preferable, on 

 many accounts. The weather is milder than in early spring, the 

 days are longer, and the fairest objects of an alpine flora are in 

 their prime. But we would with due deference recommend a 

 botanical route totally different from that which we ourselves 

 adopted. It is not to be expected that strangers would venture 

 to dictate even to the uninitiated. Yet it is to be wished that 

 young, energetic, and enterprising botanists would strike out a 

 new track for themselves, and not be contented to follow the steps 

 of scientific veterans, and continue to hunt in the same ground that 

 has for so many years been the scenes of the explorations of Don, 

 Graham, Greville, Hooker, Balfour, and their pupils and com- 

 panions. We should like to explore the hills further west, by Ben 

 More, Ben Ean, and some other of the Argyleshire mountains, be- 

 sides Ben Cruachan, the only one of these popularly known. It 

 has been stated on good authority, that the number of species de- 

 creases as the explorer advances towards the west from the east. 

 This, we have little doubt, is the case in the southern part of the 

 island of Great Britain ; and it is probably the same in Scotland, 

 from the Tweed to the Moray Frith. The agrarial annuals, or 

 colonists, as they are mostly denominated in the ' Cybele Bri- 

 tannica,^ decrease rather rapidly towards the west, because culti- 

 vation decreases. We should like to hear if the perennial her- 

 baceous plants, which do not depend on agricultm-e for their per- 

 manence, are affected by longitude ; and if so, what are the pro- 

 bable causes of this decrease. 



The rivers of the Highlands have a pretty general uniformity 

 of character. The rocky bed, the eddying pool, and the scrubby 

 or meadowy banks, are common characteristics. Of course they 

 vary in breadth, and in the quantity of water which they contain. 

 But in this even most of the Highland rivers preserve a consi- 

 derable uniformity. The lakes in which they usually originate 

 have a tendency to preserve this equality of flood. It takes se- 

 veral days' rain to raise perceptibly the surface of Loch Tay, and 



