DICECIA, ENNEAND. 289 



date lobcd toothed glabrous above downy and very white be- 

 neath, fertile catkins ovate, stigmas 4. Lightf. p. 616. 

 E. B. /. 1(518. 



HAH. In tlie Lowlands, near houses, and in plantations. Fl. Apr. T? . 



A large tree,, with smooth bark and spreading branches, of very rapid 

 growth. The wood is white and soft, and only used for coarse 

 purposes. 



2. P. tremula (Aspen\ leaves nearly orbicular broadly toothed 

 glabrous on both sides, petioles compressed, " stigmas 4, 

 auricled at the base," Sm. Lightf. p. 616. E. B. t. 1909. 



HAD. Frequent in moist woods, both in the Highlands and Lowlands. 

 Dwarfish in some of the western Isles, Lightf. Fl. April. T? . 



This tree is well known for the tremulous movement of its leaves 

 with the slightest breath of wind. This motion is aided by the 

 compressed petioles. The bark is said to be a favourite food of the 

 beavers, in countries where those curious animals still exist, and 

 the wood serves for pack-saddles, milk-pails, &c. Lightfoot tells 

 iis that the Highlanders entertain a superstitious notion that our 

 Saviour's cross was made of this tree, and for that reason suppose 

 that the leaves of it can never rest. 



3. P. nigra (black Poplar), leaves deltoid acute serrated gla- 

 brous on both sides, fertile catkins cylindrical lax, " stigmas 

 4." Sm. Light/, p. 618. E. B. I. 1910. 



HAS. Often seen about houses, and in plantations ; but a doubtful 



native, Lightf. FL. April. J? . 

 Forms a very large and tall tree of quick growth, having a light and 



not very valuable wood, as is the case with most trees that come 



soon to perfection. 



8. RHODIOLA. 



1. Rh. rosea (Rose-root). Lightf. p. 619. E.B.t.SQS. 



HAB. Upon wet rocks towards the summits of most of the Highland 

 mountains. Fl. June. If. . 



Root large, woody, which when drying gives out a smell that has 

 been compared to that of roses. Stem 6 8 or 10 inches high, 

 simple. Leaves numerous, subimbricated, obovate, thickly fleshy, 

 glaucous, serrated at the point, and in the sterile plant tipped with 

 a reddish tint. Flowers in a small terminal cyme, yellow, agreeing 

 with Sedum in every thing but the number of its parts, and having 

 a good deal the habit of S. Telephium. 



3. ENNEANDRIA. 



9. MERQURIALIS. 

 1. M. perennis (perennial or Dog's Mercury), stem perfectly 



simple, leaves rough, root creeping perennial. Lightf. p. 620. 



E. B. 1. 1872. 



HAB. Woods and shady places, common. Fl. April, May. "U . 

 About 1 foot high, herbaceous. Leaves mostly in the upper part, 



ovate, serrated, Flowers in axillary, short, lax spikes. 



