54 CONIFERAE. 



in the ordinary manner. The younger the formations which contain the 

 separate parts, and the more complete the resemblance to those of the 

 recent form which serves as a tertium comparationis, the more shall we 

 be justified in drawing the tempting but almost always hazardous con- 

 clusion that they belong to one another. 



The older formations also contain an abundance of remains of Coni- 

 ferae, but it very rarely happens that their relation to still living forms 

 can be determined with any certainty. The structural details in the cones 

 are usually badly preserved ; the number and position of the ovules, the 

 most important points, are either unknown or very uncertain. Moreover, 

 the descriptions of palaeontologists in this respect are often a good deal 

 coloured by the imagination. An instance of this is to be found in the 

 doubtful Albertia, Sch., which Schimper 1 confidently classes with Dam- 

 mara, and Schenk 2 then deals with in a similar manner. Heer 3 goes so 

 far as to say : ' The family of Abietineae appears in the Coal-measures in 

 two genera, Walchia occurring as early as the middle of the formation, 

 Ullmannia, as far as is yet known, only in its upper limits.' I shall 

 endeavour to show that nothing is known of either genus which can be 

 turned to account by the botanist, and that Heer's assertion therefore is 

 only calculated to lead those botanists, who have not occupied themselves 

 closely with fossil plants, into errors and false conclusions. And I cannot 

 say that I agree even with Schenk 4 , when he classes things like Brachy- 

 phyllum, Sphenolepidium, and Inolepis directly with the Taxodieae. His 

 criticism does not appear to me to go nearly far enough, though in other 

 respects it is thoroughly good. 



From all this it follows that our present purpose will be best served 

 by dividing the whole mass of described forms into those in which the 

 connection with living groups is botanically assured, or is of such a kind 

 that only one of these groups can be compared with them, and, secondly, 

 into those in which this connection is still doubtful ; lastly, we must briefly 

 examine the results of investigation into the fossil woods which are so 

 common in all the formations. The reader is referred to Schenk's account 5 

 for elaborate descriptions of the forms which represent our living genera ; 

 such descriptions would be unsuitable to this work, in which we are con- 

 cerned only to show what are the oldest and most certainly established 

 representatives of each of the main forms, and thus to gain some ground 

 for determining their relative age. 



The Abietineae are abundant in the Tertiaries and in the Chalk, but 

 they can as a rule be certainly determined only in their cones, or in the 

 case of the Pines in the needle-bearing branches, if these are present in 



1 Schimper (1), vol. ii, pt. i, p. 256. 3 Scheuk (1). 3 Heer (4), p. 239. 



Zittel (1). 5 Zittel (1). 



