33 



THE ANATOMY OF WOODY PLANTS 



Abietineae. This interpretation of the situation is vindicated 

 by the recent discovery of normal resin canals in the wood of 

 the axis of the ovuliferous cone of a Javanese species of Agathis, 

 A. Bidwillii (Fig. 238). 



Having discussed, so far as the limits of the present volume 

 permit, the organization of the wood in conservative axes and in 

 fossil forms, we must now turn to the discussion of that extremely 

 important organ, the leaf. It has been made clear in an earlier 



chapter that the foliar 

 organ of Pinus is char- 

 acterized by the remark- 

 able structure of its 

 fibro vascular tissues. In 

 the genus under discussion 

 and to a less extent in 

 allied genera the foliar 

 conducting strand is sur- 

 rounded by a cordon of 

 transfusion tissue. The 

 situation in this respect 

 may be clearly ascertained 

 by reference to Fig. 239. 

 The transfusion elements 

 are distinguished by the 

 absence of protoplasmic contents and by the occurrence of 

 bordered pits in their walls. It is obvious that the tissues of this 

 nature become joined with the xylem of the foliar bundles on its 

 flanks. The transfusion tissue in modern representatives of the 

 genus Pinus is not a continuous mass of tracheary cells, but has 

 interspersed throughout its substance a considerable number of 

 living cells provided with protoplasm and a nucleus. The investi- 

 gation of the Cretaceous deposits at Kreischerville, Staten Island, 

 has provided us with extremely valuable data for the determina- 

 tion of the organization of the leaf in Pinus and allied forms in 

 the later Mesozoic. In some of the numerous species of Pinus 

 which flourished in the American Cretaceous, transfusion tissue 

 was present in large amount and contained little or no admixture 



FIG. 238. Resin canal in the trace of the 

 seed scale of Agathis Bidwillii. 



