186 Mr Witham's Observations on Fossil Vegetables 



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refer in recent plants to a diversity of summers, then it is rea- 

 sonable to suppose that a similar diversicy formerly prevailed. 



" The Coniferae of the coal-formation and mountain lime- 

 stone group, have few and slight appearances of the lines by 

 which the annual layers are separated. The trees of our pre- 

 sent tropical regions have also few and slight appearances of 

 these lines. Therefore, at the epochs of these formations, the 

 changes of season were probably as little marked as they are 

 in our tropical regions. 



" Again, the condensation observed towards the outer mar- 

 gin of each woody layer of the trees of our cold and temperate 

 climates, and which is attributed to the increasing cold of the 

 latter part of the autumnal season, is decidedly observable in 

 the Coniferae of the lias ; as in Figs. 3, and 4, of the lower part 

 of Plate IV., and in Figs. 1, 2, and 3, of Plate V. Therefore, 

 at the epoch when the trees of the lias grew, there was a cold 

 season as now. 



" Between the monocotyledonous fossil and recent species 

 which I have figured, no comparison can be instituted, as they 

 are not of the same species ; but it may be remarked generally, 

 that, so far as I have examined these plants, the recent species 

 have smaller cells and vessels than the fossil. 



" The same remark is to be made of the dicotyledonous 

 woods." 



Mr Witham then remarks, that some of the recent Coniferae 

 which he has figured, are of climates similar to that in which 

 the fossil Coniferae are figured ; yet that even here no accurate 

 comparison can be instituted, as we cannot decide upon the 

 genera, much less upon the species of the fossil plants ; but that 

 in general the cells or tubes of the latter were in almost every 

 case much larger than those of the former. " Our observa- 

 tions, however, on this subject, 11 adds the author, " are not 

 sufficiently numerous or correct, to authorize any inferences as 

 to the comparative vigour of the vegetation of the different 

 epochs, although they are sufficient, along with other circum- 

 stances, to render it not improbable that the temperature was 

 higher at the periods when the fossil vegetables grew than it 

 is now. 



" The general colour of the fossil vegetables, retaining their 

 organic texture, which occur in our mountain limestone groups, 



