20 



The Scottish Naturalist. 



kinds of vegetation to which this Society devotes its energies ; so 

 that, besides the beauty we derive from these things in a very 

 small form, we owe to them in gigantic form, and in enormous 

 quantity, the great store of energy that we have in our coal mea- 

 sures, and without which the existence of civilisation and of many 

 of our arts would have been impossible. It seems to me very 

 possible that, as enormous club mosses, 50 or 60 feet high, of the 

 same general aspect as the minute ones we see in the woods here, 

 were the vegetation of the coal measures, so there was in the pre- 

 vious Laurentian era a vegetation of a lower type, of which I saw 

 the dwindled representatives on those rocks. Of course it is a 

 matter of speculation, but in all science we must begin in this 

 way with general ideas, which we must verify by facts and arguments. 



Another circumstance in connection with cryptogamic botany 

 came before me quite lately. I was anxious to discover some 

 fossils in the crystalline rocks of Argyllshire, where they seem 

 entirely wanting, although in a field of limestone of the same geo- 

 logical age in Sutherland Mr. Peach discovered fossils that proved 

 that the great mass of crystalline rocks belonged to the Silurian 

 era. The fact that no trace of life was found in the Argyllshire 

 limestone, although it was not apparently more crystalline than 

 others, was to me a great mystery, which I was anxious to solve. 

 In the course of last winter an energetic man in Campbeltown 

 sent me a specimen of limestone which he believed to be coral- 

 pitted, but which examination in Edinburgh proved to be merely 

 marked by a lichen. The mass had become covered with it, and 

 the little plants had each excavated a tiny pit, with the result that 

 the whole block closely imitated a coral. 



Passing from that, the next subject of observation which came 

 before me lately in cryptogamic botany was the appearance and 

 phenomena of the forms called Diatoms. Those organisms, 

 which can be gathered in every puddle by the roadside, have a 

 shell of pure flint, or glass, marked with beautiful patterns of an 

 ornamental nature ; and botanists and zoologists have disputed as 

 to whether they are vegetables or animals ; but whatever they are, 

 one peculiarity of those organisms is that when alive the shell is 

 filled with highly-coloured matter, generally bright green or bright 

 yellow. It is well known that some plants possess motion, but 

 those have locomotion ; and in examining them I could not 

 divest myself of the idea that they acted by will. There was this 



