92 DESC'KIFflVE CATALOGUE 



rays, which are now known to be so important a feature in the 

 diagnosis of fossil woods. 



In the genus Pity oxy Ion, particularly in the late Tertiary, are 

 species clearly to be included in the living genus Finns, and this 

 was recognised by the earlier writers. For instance, Vater (1884) 

 divided the genus Pltyoxylon into four sub- forms, to which, how- 

 ever, no varietal names were given, but their characters were 

 practically those of the modern Pines. In recent times Gothan 

 (1905) has divided the genus into two genera, Piceoxylon and 

 Pinuxylon, separating them as follows : - 



(a) Ilarzgangepithel dickwandig, verbolzt ; Mark-^ 



strahltiipfel nicht ei-porig ; Spiralverdickung Piceoxylon, Gothan 

 im Spatholz (selten auch iui Friihholz: Pseudo- .(Pityoxylon, Kraus, 

 txuga). Zahlreiche Tangentialiupfel im '. ex p. ; Pinifes, 

 Spatholz. Quertracheiden vorhanden, ohne Goepp. ex p.). 

 Zacken. Abietiueentiipfelung sehr deutlich. 



(6) Harzganijepithel diinnwandig, nur selten 



dickwandig; Markstrahltupfel (Friiliholz!) stets Pinuxylon^ Gothan 

 ei-porig. Spiralverdickung im Spatholz stets . (Pityoxylon, Kraus, 

 fehlend, ebenso Harzparenchym. Quertrachei- ' ex p. ; Pin if f,^ 

 den nut oder ohne Zacken. Abietineentiipfelung Goeppert, ex p.). 

 bei den gross-eiporigen fehlend bezw. reduziert. ) 



As Gothan points out, the name Pinoxylon, in place of Piti- 

 uxylon, would have been the natural one to take, but the generic 

 name Pluoxyloti had been used by Knowlton (1900) for a very 

 poorly illustrated specimen of Jurassic age. His diagnosis of 

 that genus is as follows : " Internal structure of the wood 

 same as in Finns, except in the absence of fusiform rays." 

 But, as Gothan (1908) points out, this absence really portends 

 the absence of horizontally nuininy resin-canal^ and conse- 

 quently the wood is not the same as recent Pmus, in which the 

 presence of both vertically and horizontally running resin-canals 

 is a universal feature and one of first-rate diagnostic signifi- 

 cance. As has already been observed, the wood described by 

 Knowlton appears to belong to the genus Protopweoxylon, 



I agree with Jeffrey & Chrysler (1906) that this division of 

 Pityoxylon by Gothan does not serve a useful purpose, while 

 the wider scope of the old generic name is more in accord with 

 the range of variation possible in the earlier members of the 

 group. 1 have therefore not adopted Gothan 's sub-divisions, 



