Senry Woodward — Old Land- surfaces. 497 



Mr. Newton, that these spore-cases were buried in the shed spores 

 themselves, and both together make up the substance of this most re- 

 markable deposit of Coal. But in readily accepting this interesting 

 discovery, let us guard ourselves against the tendency of all modern 

 scientific generalizers who take up ideas as soon as issued from the 

 mental mint, " and run into extremes ;" for, admitting that a giant 

 Lycopod Forest in the Coal-period would, in the course of years, 

 probably shed several times its actual tree-and-branch-bulk of seed- 

 spores, yet it most probably shed its leaves as well as its spores and 

 its wood-growth, and that of the forests of giant Calamites and 

 ferns around would amount to an enormous mass in the course of 

 ages of accumulated growth and decay, such as the Coal-forests 

 reveal to us. The tiny acicular leaves of a pine-forest of to-day 

 often form a mass several feet in thickness beneath and around the 

 parent trees, which needs but the proper accessory circumstances to 

 convert it into Quaternary Coal. 



Of the three hundred plants which occur in the Coal-period we 

 know but little, whilst a great part of the vegetation has probably 

 left no sign. For experiments made long ago by Dr. Lindley go far 

 to prove that most vegetable tissues break up with great readiness 

 and become completely disorganized when saturated under water. 

 Thus he found that after two years submersion beneath freshwater, 

 121 out of 177 species of plants had entirely disappeared; and of 

 the fifty-six remaining, the most perfect were Conferee, Palms, 

 Ferns, and Lycopodiacece. There are probably no palms in the 

 Coal-measures, but remains of the other three classes are most 

 abundantly preserved, which lends strong confirmation to Dr. 

 Lindley's experiment. 



Formerly, it was supposed necessary, in order to account for the 

 rich deposits of carbonized vegetable remains in the Coal, to assume 

 a tropical temperature with a damp humid atmosphere, composed in 

 gi'eat part of carbonic acid gas. 



Indeed, surprising as it may seem, so lately as May, 1869, this 

 doctrine was advocated by an eminent chemist, Dr. T. Sterry Hunt, 

 F.E.S., in a lecture delivered before the Eoyal Institution (see 

 Eeport, Geol. Mag., Yol. IV. pp. 357-369). He there stated— 

 " With regard to the composition of this earlier atmosphere — un- 

 fitted as it was for the higher forms of life, still from the compara- 

 tively large amount of carbonic acid present, it would seem to have 

 been peculiarly fitted for the development of luxuriant vegetation ; 

 and it was long since pointed out by Brongniart that we might sup- 

 pose a marvellous luxuriance of vegetation in earlier periods of the 

 earth which gave rise to enormous beds of coal and other fossil fuel ; 

 for we should judge that this abundance of carbonic acid favoured a 

 wonderful development of vegetation, and at the same time the 

 elimination of the carbon in the shape of coal would heljD powerfully 

 to purify the air at that time." ^ He further suggests that this dense 

 canopy of carbonic acid gas " would permit the solar heat to pass 



1 Later experiments have, however, proved that plants, like animals, are at once 

 poisoned by an excess of carbonic acid. 



VOL. Tin.— NO. LXXXIX. 31 



