PLANT REMAINS. 123 



Subdividing still further, according to their most marked 

 characteristics, whether external or internal, the botanist 

 arranges all the known forms of Vegetable Life into some 

 300 orders, upwards of 9000 genera, and about 120,000 

 species. As the most of these distinctions, however, are 

 founded on the form and connection of the flower, fruit, 

 and leaf organs which rarely or never occur in connection 

 in a fossil state the palaeontologist is guided in the main 

 by the great structural distinctions above adverted to, and 

 not unfrequently by the simple but unsatisfactory test of 

 "general resemblance." The flower and the organ of 

 fructification may have perished, but still the form and 

 venation of the leaf, the external sculpturing of the bark, 

 the disposition of the leaves and branches, and the general 

 mode of growth, may be preserved; and from these, as 

 well as from a microscopic examination of the lapidified 

 tissues, the palseophytologist can for the most part deter- 

 mine, or at all events approximate to the determination of, 

 his fossil twigs and fragments. So certain, indeed, are the 

 determinations of the microscope, that where good sec- 

 tions can be procured, the competent observer rarely or 

 never fails to establish the great order to which the or- 

 ganism belongs ; and this, considering the difficulties 

 surrounding pala30phytology, is a triumph of no mean 

 description. 



As the palaeophytologist, in arranging his fossil organ- 

 isms, is guided by the classification of the botanist, so the 

 palaeozoologist follows, as closely as the nature of his ob- 

 jects will permit, the systematic schemes of the zoologist. 

 And in this he has altogether an easier task, inasmuch as 

 animal organisms, from their less destructible nature, are 

 in general more perfectly and legibly preserved. The 

 horny and calcareous structures of zoophytes, corals, shells, 

 crusts of Crustacea, calcareous tubes of annelids, chitonous 



