FIBROVASCULAR TISSUES: RAYS 



73 



clearly tracheary in their character, since they contrast with the 

 adjoining elements both in the absence of protoplasmic contents 

 and in the occurrence of bordered pits in all their walls. It is 

 evident that in the case under discussion short tracheids may make 

 their appearance among the elements of the radial parenchyma as 

 a sequel to injury. The interesting investigations of Miss Holden 



FIG. 53. Ray from the injured root of Sequoia gigantea. Explanation in the 

 text (after Holden). 



on the Cupressineae and Taxodineae as a whole make it clear that 

 abnormalities of this kind in these subtribes of coniferous gym- 

 nosperms are a common feature in the wood formed after injury. 



It follows from the statements and illustrations in connection 

 with the last paragraph that normally in Chamaecyparis noot- 

 katensis and traumatically in practically all representatives of the 

 Cupressineae and Taxodineae, ray-tracheids are found such as 

 are a feature of the normal structure of the wood in the lower 

 members of the Abietineae. The most natural interpretation of 

 this phenomenon is in connection with the biological doctrine of 



