Facts relating to the Tormentilla officinalis. By Dr R. D. THOMSON. 



THE following tables have been drawn up from observations on the 

 Tormentilla officinali^ which were made with the view of contributing 

 to the determination of a question which has interested most botanists 

 whether the genus Toririentilla should be considered as distinct from 

 Potentilla, or whether the species of the former genus should be ranked 

 under the latter. I have seen observations somewhat similar, but upon 

 a less particular plan, than those I have detailed, for nothing has hither- 

 to been related regarding the soils upon which the different specimens 

 examined had vegetated, which must be considered of very considerable 

 importance in determining the effect of soil in increasing or diminishing 

 the number of petals. The plants subjected to examination were col- 

 lected on four distinct formations, viz. 1. Mica-slate, 2. Old Red Sand- 

 stone, 3. New Red Sandstone ; and, 4. Diluvium. By the latter term 

 is to be understood the grav e 1 left by the retiring of Loch Lomond, on 

 the west side of that lake, on the road from Helensburgh to Luss, which 

 passes through numerous artificial-looking tumuli, presenting a rounded 

 outline. A careful search satisfied me that these were formerly islands 

 in the lake, similar to those which now vary so beautifully its surface, and 

 which have been left as isolated hillocks by the gradual draining of the 

 lake. The gravel consists of clay -slate. The new red sandstone at Helens- 

 burgh is formed of fragments of clay-slate, imbedded in clay, obviously 

 a product of the disintegration of the clay-slate rocks, and is overlaid in 

 general by a stiff reddish soil. The new red sandstone of Berwick- 

 shire appears to be closely connected with the carboniferous series. 

 These observations seem necessary in order that the subsequent facts 

 may be better appreciated. 



