482 STUDIES IN FOSSIL BOTANY 



the pith (Fig. 177, d and e). The secondary wood has 

 a dense structure, with narrow medullary rays, one or 

 at most two cells thick, and resembles that of the 

 Cordaiteae (see Chapter XII.). The "tracheides bear 

 multiseriate bordered pits. An interesting peculiarity 

 is the presence of wide and short tracheides in the inner 

 layers of the secondary wood ; presumably they served) 

 like the similar primary tracheides of Megaloxylon 

 and Zalesskya, for water-storage, but here they form 

 part of the secondary tissue-system. 



Another species, Calamopitys Beinertiana} occur- 

 ring in the Calciferous Sandstones of the Tweed, 

 and at Falkenberg, in Silesia (Lower Carboniferous 

 or possibly Devonian) is remarkable for the large pith, 

 containing " sclerotic nests "' like those of Lyginodendron. 

 The numerous primary xylem-strands resemble those 

 of the last species, except in the interesting fact that in 

 the lower part of their course they become endarch, 

 losing their centripetal wood altogether — a first ap- 

 proach towards the structure of the typical Gymno- 

 sperms. In this species a scale-bark was formed on 

 the older stems. 



The Calamopityeae show clear affinity with Lygino- 

 dendron in the structure and arrangement of the primary 

 strands of wood ; in the secondary wood they approach 

 nearer to the Cordaitean type ; the structure of the 

 petioles (not yet investigated in sufficient detail) is 

 peculiar, and rather recalls Medulloseae than Lygino- 

 dendreae. The family evidently formed one branch of 



1 The Araucarites Beinerlianus of Gbppert. See Scott, I.e. p. 341. 



