ENUMERATION OP CONIFEROUS PLANTS. 



47 



found large masses of carbon deposited in the earth in the form of 

 beds of " brown coal," or lignite, which are almost entirely composed 

 -of Coniferous remains. " But these Coniferous forests did not exhibit 

 a dull uniformity, as is the case with those of the present time, 

 there was, on the contrary, an abundant and cheerful variety of forms, 

 as is seen even now in the forests of Canada and Asia, though not 

 to so great a degree. There must also have been enormous quantities 

 of resin exuded by some of these trees which belonged to genera 

 resembling Thuia and Cupressus ; the resin, hardened by external con- 

 ditions, being now known as amber." * 



The higher we ascend in the Tertiary strata, the nearer do we find 

 forms of vegetation approaching those now existing. In Italy has 

 been found the remains of Ginkgo (Maiden Hair), the only present 

 ally of which grows in China and Japan ; and in the forest beds 

 near Cromer, in Norfolk, have been found cones, foliage, and wood 

 of Pinus sylvedris, Allies excelsa, and Taxus baccata, all. common 

 living species, t 



The number of existing genera and species of Coniferss has been 

 variously estimated The late Mr. Andrew Murray, in the Gardeners' 

 Chronicle for 1866,| gives the following enumeration arranged according 

 to the geographical distribution. 



Reckoning Pinus, Abies, Picea, Larix, and Cedrus, as distinct genera, 

 and Cupressus, Chamaecyparis, and Retinospora as one. But as several 

 genera occur in more than one of the regions here specified, Pinus, 

 for example, in four, Abies in three, Larix in three, Podocarpus in 

 five &c, it is evident that the total represents a considerable excess 

 in the number of genera. Oh the other hand, the total number of 

 species, three hundred and twenty, represents nearly the number actually 

 known. 



* Thome"s Structural and Physiological Botany, p. 430. 



f Dr. Ramsay's Physo-Geology of Great Britain, p. 134. 

 ? p. 634. 



