Scientific Lectures. 73 



growth of a forest of Sigillaria. The next class of plants is the 

 Calamites. Some one called upon a botanist, said he had been shown 

 his "calamities and felicities." These Calamites were the calamities. 

 They seem to have grown on muddy flats along the margin of the 

 Sigillarian woods, resembling Eqniseta, or mare's tails, and they are 

 still preserved in coal formations, in large numbers, in the erect posi- 

 tion. The Calamites seemed to have preserved the Sigillarian forests 

 from the effects of inundation, by causing the mud to settle before the 

 waters passed into the forests. The Calamites thus contributed very 

 much to the purity of our coal beds. The next plant is the Lepido- 

 dendron, or scale-tree, of a size equal to the Sigillaria, resembling our 

 ground pines or club-mosses. This tree was more plentiful in the 

 earlier coal formations than in later periods. (Other plants, also 

 found in beds of coal, were described by Professor D., and drawings 

 of them on a large scale were shown.) The plants of the carbonifer- 

 ous period would have presented to our eyes a very monotonous 

 appearance ; for it was characteristic of the flora of that period, that 

 there was a large number of species but few genera, and these very 

 uniform in their foliage. There were also some plants more familiar 

 to our eyes. The ferns are to be found in the roofs of the coal beds, 

 preserved as beautifully as they could have been preserved in a her- 

 barium. They resembled more closely the ferns of New Zealand or 

 the Hebrides, than the ferns with which we are familliar. Some of 

 the tree ferns grew to the dignity and beauty of the palm tree itself. 

 One genus, Megaphyta, was peculiar, lia\'ing only two leaves at a 

 time. We find, sometimes, in the coal beds things looking like enor- 

 mous brooms, which are tree ferns, with roots sent out to strengthen 

 the stems (Psaronius). We also find in the coal formation species of 

 pine, the wood of which much resembled our modern pines. It is 

 remarkable that the pine is very widely diffused at the present day, 

 and it is not wonderful, therefore, that they should have existed in 

 the carboniferous period. These pines have features more nearly 

 resembling those of Australia and N"ew Zealand, than those of our 

 climate. When wood is buried in the earth, and its cells filled with 

 water, holding silica or lime in solution, they become filled with stone 

 and the wood becomes coal ; and this is the form in which we find 

 these fossil remains. By removing the mineral, we can observe 

 the vegetable structure of the plants, and determine their character. 

 Kext to the soil on which we tread, the most valuable substance we 

 have is mineral coal, which is derived from the plants of the carbon- 



