[PKNHALLOW] NOTES ON TERTIARY PLANTS 37 



somewhat abundant resin they contain. Resin canals are altogether 

 absent, but resin cells are both numerous and conspicuous. In the 

 spring wood they are well defined by virtue of the dark resin masses 

 which they hold, and there is reason for the belief that they fall into, 

 more or less well defined tangential bands such as constitute so char- 

 acteristic a feature of Taxodium. In the summer wood, the resin 

 cells lying along the inner face are not infrequently located in well 

 defined bands. Throughout the greater extent of the summer wood 

 where they are abundant, they are usually devoid of resin and are 

 then to be recognized as empty or nearly empty cells which thereby 

 acquire great prominence, in an otherwise reddish-yellow tissue. 



The longitudinal sections were found somewhat difficidt to study 

 on account of the dislocation of parts. Nevertheless, the radial sec- 

 tions show the medullary rays to be devoid of tracheids; but the most 

 significant fact for diagnostic purposes is the occurrence on the 

 lateral walls of the ray cells, of distinctly bordered pits. These struc- 

 tures are 1-2 per traoheid, oval or round and with a lenticular-oblong 

 «orifice which is diagonal to the axis of the ray. When the pits are 

 two in number, they fall into radial series. These facts point without 

 question to the general affinities of the plant, and show that it is 

 beyond all question one of the Taxodiese. 



In his original description of these plants, Sir William Dawson 

 specifies Cupressinoxylon, species (c), which may be the same as the 

 one now in question, as he says it approaches the wood of Taxodium 

 or Cryptomeria, but " it may have belonged to Glyptostrobus." ^ Now, 

 the genus Taxodium has hitherto been wholly unknown to these de- 

 posits through its wood, and to a very limited extent only through 

 its foliage, and there is, therefore, very little to support the assumption 

 that this is the wood of a true Taxodium except the evidence to be 

 derived from the internal structure, and this is so similar that there 

 seems to be little room for hesitation. On the other hand, however, 

 the alteration of structure by decay and compression is such as to lead 

 one to exercise caution in expressing a final opinion in a case where 

 comparatively slight difi'erences, readily obscured by such conditions 

 of preservation as are here represented, might make all the difference 

 between one genus and another. Glyptostrobus europœus is a well 

 recognized species of the Porcupine Creek and Great Valley Series 

 as recorded by Sir William Dawson, where it has been identified through 

 its leaves.- The very close relationship between Glyptostrobus and 

 Taxodium at once directs attention to the possibility that the wood 

 belongs to the former, rather than to the latter genus. 



' B. N. A. Bound. Comm., 1875, App. 331. 

 =" Ibid., 328, 329. 



