upon Native Vegetables. 37 



itself, which is, Whether or not vegetable specks are regulated 

 by the subjacent rocks? or, in other words, Whether native 

 plants, or a majority of them, spring up and thrive upon all 

 rocks indiscriminately, when other circumstances are favour- 

 able ; or, if they do so, some only over one rock, and others only 

 over another ? The interest belonging to the subject entitles it 

 at least to consideration ; and notwithstanding the formidable 

 objections to the doctrine, there is undoubtedly, even on the 

 part of individuals whose opinions deserve much respect, an in- 

 creasing disposition to believe, that the indigenous vegetables 

 are frequently capable of disclosing the nature of the rock that 

 lies beneath them *. 



An obvious difficulty presents itself in the consideration, that 

 though relations of the kind alluded to did in reality exist, no 

 one can hope ever to be able to specify in words the nature of 

 the connexion. This is certainly true, provided mineral masses 

 be viewed through the medium of the present systems ; wherein 

 the same name is often given, and perhaps of necessity, to sub- 

 stances widely different in structure and composition ; and 

 wherein rocks are arranged and distinguished according to posi- 

 tion and connexions, rather than according to qualities by which 

 vegetables are likely to be influenced ; these qualities being the 

 nature of the component parts of the rock, together with its 

 tendency to be converted into soil. Thus granite, it is well 

 known, at one time completely resists the weather for ages, 

 while at another it readily furnishes an abundant soil. Basalt, 

 too, is occasionally of the most obdurate description, though in 

 general it is copiously converted into one of our most fertile 

 earths. It is almost unnecessary to add, that in the case of sand- 

 stones, conglomerates, breccias, and of amygdaloids, it must be 

 impossible to discover any unvarying relation between vegetables 



• It has been also thought, that the native vegetation may indicate the 

 qualities of soils; and, indeed, attempts have been made to draw from the 

 same source several curious inferences. Of these, one of the most interest- 

 ing has been noticed by Clarke, the traveller, respecting Arundo Phragmites, 

 a plant not uncommon in this country, and other parts of Europe; and the 

 observation may be here mentioned, though not strictly connected with the 

 present object. " Another criterion," says he, " of the sources of mephitic 

 exhalation, is the appearance of Arundo Phragmites. This plant in warm 

 countries may be reckoned a warning buoy." 



