CEDROXYLON 213 



Mataram formation as exhibiting the features of Parace- 

 droxylon. 



VI. CEDROXYLON. Kraus. 



This generic name was instituted 1 for fossil wood agreeing with 

 Cupressinoxylon in the arrangement of the pits on the tracheids 

 and in the absence of resin-canals, but differing in the scarcity or 

 absence of xylem-parenchyma. As defined by Schenk 2 , Cedroxylon 

 stands for fossil wood agreeing generally with that of recent species 

 of Cedrus, Abies, and Tsuga with or without tracheids in the 

 medullary rays. Brongniart's genus Eleoxylon 3 is included by 

 Schenk as a synonym of Cedroxylon. The chief distinguishing 

 character of Cedroxylon as compared with Cupressinoxylon, as 

 used by some authors, is the more restricted occurrence of xylem- 

 parenchyma ; in Cedroxylon it is confined to the end of each year's 

 wood whereas in Cupressinoxylon the parenchyma is not so limited 

 in its distribution. A closer examination of different types of 

 wood included in Cedroxylon shows that the xylem-parenchyma 

 is an unsafe guide: Barber 4 states that he found more xylem- 

 parenchyma per square millimetre in Cedrus wood than in Crypto- 

 meria (a genus included in the general term Cupressinoxylon) and 

 Lignier 5 speaks of the absence of parenchyma in some species of 

 Cedroxylon. Gothan 6 , who has discussed the distinctive features 

 of these and other genera in considerable detail, points out that 

 in Abies Webbiana xylem-parenchyma is abundant as in Cupress- 

 inoxylon, while in some Cupressineae the parenchyma is so scarce 

 that it is often difficult to discover. It is clear that a test based 

 on the presence or distribution of xylem-parenchyma is unsatis- 

 factory ; the application of such a test would lead to the inclusion 

 of both Abietineous and Cupressineous genera in one generic type. 

 In typical cases the distribution of xylem-parenchyma is none 

 the less a useful character, but Conifers with parenchyma scattered 

 through the year's growth are not confined to types usually in- 

 cluded in the comprehensive genus Cupressinoxylon : many Podo- 

 carps and some other genera not members of the Cupressineae 

 possess abundant parenchyma in the wood. The structure of the 



1 Kraus in Schimper (72) A. p. 370. 2 Schimper and Schenk (90) A. p. 862. 

 3 Brongniart (49) A. p. 76. 4 Barber (98) p. 332. 



5 Lignier (07 2 ) p. 245. Gothan (05) p. 45. 



