134 The Scottish Naturalist. 



gically the county is divided into two great districts by a line 

 running from south-west to north-east, the part to the south of 

 this line belonging to the Devonian formation, and the part to 

 the north to the Silurian. The Devonian district consists of 

 a wide plain or valley of Old Red Sandstone, intersected by 

 numerous trap dykes, and bounded on the south and east by 

 two ranges of trappean hills — that to the north of the Tay being 

 known as the Sidlaws, while the one on the south is the Ochil 

 range. In Perthshire these hills rarely attain an altitude of 

 1 200 feet, and their flora is consequently scarcely at all alpine 

 in character. The Devonian district is in fact co-extensive 

 with the Lowland part of the county, and is a cultivated and 

 fairly well-wooded country. The higher parts of the Ochils and 

 Sidlaws are uncultivated, but extensively grazed by sheep ; are 

 not as a rule covered by wood ; and their more interesting flora 

 is to be found in the ravines. The Silurian division, on the 

 other hand, is essentially a hilly country, and is co-extensive 

 with the Highland part of the county. In it the only culti- 

 vated portions are the valleys, which for the most part are not 

 very wide, the hills themselves being, as is most generally the 

 case, covered with heather or grassy pasture, and more rarely 

 with natural or planted woods. But though this is a region of 

 hills, it is only in certain parts that the necessary conditions for 

 the existence of the alpine flora are all to be found, and it is on 

 the hills to the north and west of Loch Tay that this flora is to 

 be found in its greatest perfection. 



The county has no sea-board, but the Perthshire shores of the 

 estuary of the Tay afford the necessafy conditions for some of 

 the maritime plants. Hence in the Carse of Gowrie district, a 

 number of plants are to be found that do not occur elsewhere in 

 the county. 



In the following list, in addition to the truly indigenous plants, 

 some of the better established or more widely spread aliens or 

 naturalised plants are noticed. 



RANUNCULACE^L 

 1. Thalictrum L. 



1. Alpinum L. Local, but not uncommon on the richer hills. 



2. Minus L. 



i. Sub-species minus L. 



Var. montanum Wallr. Local, but widely distri- 

 buted. 



