The Scottish Naturalist. 



293 



as the Saxifraga occurs on the shores of some of the lowland lakes, 

 — to which it appears not to have been brought by water, — it 

 may have come from them. Some other alpine species might 

 have been expected to occur on the shingles of the Tay, since 

 they grow on the banks of some of the tributary hill-streams ; but 

 they have not yet been detected. Some of them have been found 

 on the shingles of other northern rivers. 



Instead of attempting to enumerate all the species that occur 

 on the shingles and stanirs, it will be more instructive to give a 

 brief account of one locality which at present shows all the stages 

 of the life-history of these formations. This is the Woody Island, 

 a combination of shingle and stanir, situated in the Tay about 2 

 miles above Perth. Its flora has been carefully investigated by 

 my friend Mr. William Barclay, who has published an account of 

 it in the Transactions of the Perthshire Society of Natural Science 

 (Vol. I. p. 30.) 



The area of the Woody Island is now about seven acres, though 

 a few years ago it was considerably greater. On the east side it 

 is being rapidly destroyed by the river, but, to compensate for 

 this denudation, it is growing — though rather slowly — towards the 

 north. The surface of the lower end of the island is about 12 

 feet above the level of the water when the river is low, but the 

 northern part is not nearly so elevated. When the water is low the 

 northern part of the island is connected by a dry shingle with the 

 west bank of the river ; but in the time of floods the river not 

 only surrounds the island, but fills a shingly channel which divides 

 it into two. In very high floods a considerable part of the island 

 is submerged. While the substratum is of the usual nature of 

 all stanirs, being formed of shingle, gravel and sand, the upper 

 layers consist of a humus sufficiently rich to support a very 

 luxuriant vegetation. 



Whilst the area extends, as has been said, to about seven acres, a 

 considerable part (probably more than half) is covered with such 

 a dense growth of planted spruces that but few other plants are 

 able to grow. Consequently the space available for the rich flora 

 is very considerably less than the total area of the island. That 

 the flora is a rich one will, I think, be admitted, when I state that 

 our explorations have resulted in a list of upwards of 330 flower- 

 ing plants and vascular cryptogams. The greater part of these 

 consists of species indigenous to the banks of the Tay and its 



