CHAPTER VIII 



WOOD PARENCHYMA 



In our present studies we recognize as wood parenchyma all 

 those elements which, in association with tracheids, have their 

 major axes extended parallel with the principal axis of growth ; 

 and which, in accordance with accepted limitations, are charac- 

 terized by their more or less cylindrical form, abrupt termina- 

 tions, and relatively thin walls. Such elements do not occur in 

 wood of the Cordaitales, and they are infrequent in the Ging- 

 koales, but they are somewhat conspicuous features of the Coni- 

 ferales, where they acquire great prominence either because of 

 their peculiar contents or their association with somewhat highly 

 specialized tissues. They differ in their structure as in their 

 special functions, though in the main they are connected with 

 the production of resinous matter ; and inasmuch as their most 

 prominent feature is usually found in associated products of cel- 

 lular activity, it will be most convenient to discuss them under 

 specific names, which may serve to direct attention to their par- 

 ticular purposes in the plant economy. They may therefore be 

 classified as follows : 



Wood parenchyma : 



a. Crystallogenous idioblasts. 



b. Resin cells. 



CRYSTALLOGENOUS IDIOBLASTS 



The investigations of Eichler (15, 35) show that in Gingko 

 the wood is characterized by the presence of wood-parenchyma 

 cells, which take the form of short idioblasts of lenticular form 

 in longitudinal section, and are distinguished by the storage of 

 crystals of calcium oxalate. Such structures are peculiar to this 



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