2()G Dr. A. Voclcker on the Comjwsition of 



mies,) from observation. On a single tree I counted thirty 

 specimens within reach. When I examined this neighbourhood 

 early in the previous iMarch, the ground was dry, as well as the 

 vegetation ; //. hcemastoma was only to be obtained by getting a 

 Cingalese to climb trees in their search, and but a single flat 

 slug (probably a Vaginulufs) was to be found under stones : before 

 my second visit the sun had passed to the north of the island, 

 aud the consequent showers had liberated the testaceous tribes 

 from their hiding-places. With reluctance I quitted a field so 

 imperfectly explored by conchologists, and where doubtless other 

 new species remained to reward researches uninfluenced, as mine 

 were, by the warning flag and rising smoke of the Suez steamer. 

 One of the specimens of Helix hcemastoma laid a single egg 

 while in my possession. In its calcareous covering and size*, it 

 resembled that of a small bird. It formed a curious contrast 

 with the numerous small ova, with a pergamenous integument, 

 extruded, in a mass, by the large Mauritian Achatina Ftdica, a 

 shell possessed of a much more extensive aperture. The name 

 given to a shelled snail, by the Cingalese at Galle, is " Gombela." 



Aix la Chapelle, Feb. 22nd, 1851. 



XXV. — On the Composition of the Ash of xlrmeria maritima, 

 growing in different localities, ivith remarks on the geographical 

 distribution of that Plant ; and on the presence of Fluorine in 

 Plants. By Dr. A. Voelcker, Professor of Chemistry in the 

 Royal Agricultural College, Cirencesterf. 



The relation of the inorganic constituents of the soil to the 

 plants is exhibited in a very distinct manner by those plants 

 which are confined to perfectly distinct geognostic formations ; 

 for it is evident that their growth is influenced in a great mea- 

 sm'e by those inorganic matters found in their ashes, which form 

 constituent parts of the soil upon which they grow. If we find, 

 for instance, that a plant which requires a considerable quantity 

 of common salt for its perfect development will not thrive in a 

 soil destitute of common salt, or that plants the ashes of which 

 have been found to contain invariably a certain amount of phos- 

 phoric acid, do not grow vigorously on land which contains few 

 traces of this acid ; further, if we find the condition of such 

 plants greatly improved by the addition of common salt or phos- 

 phoric acid to their respective soils, we cannot remain doubtful 

 for a moment as to the cause of the failure in the first instance. 

 There are however very few plants characterized by particular 



* Lciijrfh -rVi- <liaiii. 55 inch. 



t Road before tlic Botanical Society of Edinbiugb, Feb. 13, 1851. 



