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THE POPULAR SCIENCE MONTHLY. 



With the Devonian things changed. The bad state of preservation 

 of fossil vegetables belonging to this formation has not permitted us 

 to study them perfectly ; but, from the aspect of those which we pos- 

 sess, we conclude that at this epoch the vegetable kingdom was al- 

 ready vigorous and varied, and that nature while in its infancy put 

 forth the carboniferous flora, the almost inconceivable exuberance of 



Fig. 4.— Phimobdiai Teerestbial Plants observed bt M. Lesquereux in the Upper Silurian 

 OF America : I. Psilophyton cornutum. (Lesquereux). 2-4. Syheno'phylluin pritnosis- 5. Annu- 

 laria Bomingen. tj. Protostigma sigillarioides. 



which has never since been equaled. This flora, to the description of 

 which numerous works have been devoted, is still more interesting and 

 important as furnishing the elements of the coal — the soul of industry, 

 as it has so justly been called. "We know that the conditions in which 

 the coal-beds were formed very much resembled those in the midst of 

 which the peat is now actually being formed. As Saporta has ob- 

 served, in the Carboniferous epoch there were emersions upon a grand 

 scale, emersions succeeding each other, flowing over and receding from 

 the insular or continental space, until its recovery from the waters. 

 This action of the waters would produce a low bank or shore around 

 the primitive land, the relief of which would tend to become more 

 accented, and at length would retain the waters coming from the inte- 

 rior and unite them at the bottom of extensive depressions. In this 

 way were formed vast lakes, with vague banks and shallow waters, easi- 

 ly invaded by plants loving an aquatic station. If we join to this the 

 humid warmth, the thickness of the atmosphere, charged with vapors, 

 causing frequent and violent rains, we perceive how favorable were 

 the conditions for the development of the carboniferous vegetation. 



The plants of this flora belong exclusively to the two classes 

 of vascular cryptogams and gymnospermous phanerogams. At the 

 head of the cryptogams were the Calamarias, which recall on a gigan- 

 tic scale the Equisetaceoe of our day ; by their side Asteraceae, Annu- 

 laria, Sphenophyles ; then come ferns of very varied form and struc- 

 ture, and Licopodiaceae of the type Lepidendroidese. Certain plants, 

 the Bornia, Calamodendreoe, and Sigillaria, form connecting links be- 

 tween cryptogams and phanerogams. These were gymnosperms, that 

 is, plants assimilable by the class Ci/cadece to the conifers and the ac- 



