THE ANATOMY OF THE CONTFERALES. 



D. P. PEN HALLOW. 



Resinous Tracheids and Resin Cells. 



The investigations of Eichler (ii, p. 35) show that in Ginkgo 

 the wood is characterized by the presence of wood parenchyma 

 elements which take the form of short idioblasts of a lenticular 

 form in longitudinal section, and are distinguished by the stor- 

 age of crystals of calcium oxalate. These structures are pecu- 

 liar to this genus in which they form a specific character of 

 definite value, but a more detailed account of them at this time 

 is not called for. 



In a large proportion of the Coniferales the wood is charac- 

 terized by the presence of more or less numerous wood-paren- 

 chyma cells. These are always distinguished by their cylindrical 

 form and transverse terminations. They are invariably associated 

 with the production of resin, either as entering into the compo- 

 sition of resin passages, or as isolated cells. It is this latter 

 group with which we are most particularly concerned at the 

 present moment and as, with very few exceptions, they are uni- 

 formly characterized by the presence of resin which gives them 

 a distinctive appearance, I prefer to describe them as resin 

 cells" rather than by the more commonly employed designation 

 of "wood-parenchyma," which conveys no suggestion of their 

 special function and most prominent feature. 



Before proceeding to consider these structures more in detail, 

 it will be necessary to digress for a short time and discuss certain 

 other elements which have been erroneously regarded as wood- 

 parenchyma. It has been stated by Eichler (i i, p. 35) that 

 wood-parenchyma elements occur in Araucaria and Agathis, but 

 this is evidently due to a wrong interpretation of certain features 

 presented by species of those two genera, which, according to 

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