242 



CONIFEBAIiES 



[CH. 



(fig. 730, C) in the field resemble those of some Pines and other 

 Abietineae as also those of Sciado-pitys (fig. 693, N) : in Xenoxylon 

 there are no resin-canals and no xylem-parenchyma. Grothan 

 considers that while differing in the sum of its characters from any 

 other type of Conifer, Xenoxylon shows most resemblance to 

 Gothan's genus Phyllocladoxylon (= Mesembrioxylon Sew.)^, a genus 

 including fossil species which suggest affinity not only with Phyl- 

 locladus but with other members of the Taxaceae. In his account 

 of Xenoxylon phyllocladoides from King Charles Land Gothan 

 describes instructive examples of the efEect of the action of fungal 

 hyphae on the structure of tissues. The genus may be described as 

 a generalised type exhibiting features shared by the Araucarineae 

 and Taxaceae. 



XIII. ANOMALOXYLON. Gothan. 



Anomaloxylon magnoradiatum Gothan. Gothan proposed this 

 name for some Upper Jurassic wood from Spitz- 

 bergen^ which cannot be definitely assigned to a 

 family-position : its most striking feature is the 

 occurrence of large spindle-shaped medullary 

 rays containing a large 'canal,' or spaces lined by 

 a single layer of cells (fig. 731). The rings of 

 growth are well marked, the summer-wood 

 being composed of avery few rows of tracheids 

 in abrupt juxtaposition to the larger spring 

 elements, a character associated with roots. 

 There are no vertical resin-canals and no regular 

 or typical horizontal canals. Xylem-parenchyma 

 is rare or absent. The bordered pits on the 

 radial walls of the tracheids are in 1 — 2 rows, 

 separate and circular or, more frequently, con- 

 tiguous and more or less flattened but, if in two 

 rows, not alternate. The medullary rays are 

 uniseriate, generally 5 — 7 cells deep, or in places 

 forming broad and deep spindle-shaped areas 

 either empty or containing a large circular canal- 

 like passage. These peculiar rays, as seen in a 

 tangential section of the wood, are a conspicuous feature and are 



Fig. 731 

 xylon 

 alum. 



t 111 



Ani/malo- 

 inagnoradi- 



MeduUary 

 ray showing the 

 sraaU cells and a 

 resin-canal. (After 

 Gothan. ) 



* See page 203. 



Gothan (10) p. 10, PI. i. figs. 9—11; PI. ii. figs. 2, 3. 



