310 The Botanical Gazette. [November, 



ciently when brought into direct relation with the phloem and 

 its proteid contents. 



44 In concluding we-wish to point out the bearing of our sub- 

 ject on a theory which has recently been put forward as to 

 the function of the phloem in general. In opposition to the 

 prevailing view that the phloem is primarily a conducting 

 tissue for the nitrogenous and especially for the proteid food- 

 substances of the plant, Prof. Frank and Dr. Blass maintain 

 that the phloem is essentially a store tissue for the benefit of 

 the wood. (See this journal xv. 346.) 



"We purposely avoid criticising Dr. Blass' arguments. 



We willingly admit that in all plants with cambial 

 growth, the supply of food materials for such growth must be 

 an important function of the phloem. . . . But we wish 

 to point out that the anatomical relations of the phloem are 

 often quite inconsistent with the supposition that its principal 

 or exclusive function is connected with the formation of wood. 

 44 In all the numerous plants which have bicollateral bun- 

 dles or an analogous arrangement of tissues, a great part of 

 the phloem, often the greater part, and sometimes nearly the 

 whole, is placed in that region of the stem where no forma- 

 tion of wood is going on, in a position as remote as possible 

 from the wood-producing cambium, for the rare exceptions 

 in which internal wood is formed may here be left out of con- 

 sideration. Yet this internal phloem is absolutely typical in 

 structure and contents. 



44 So too with the phloem islands. In plants like Strych- 

 nos, these are no sooner formed than they become imbedded 

 in dense wood, and are cut off from all direct communication 

 with the cambium. It would be easy to cite other examples, 

 as the stems of the Chenopodiacere and many other allied or- 

 ders, in which almost all of the phloem is deeply imbedded 

 in the fully-formed wood, or the monocotyledons generally, 

 where the closed bundles retain a typical and active phloem 

 for months and years after all formation of wood has been 

 completed. 



44 In the light of facts such as these, we cannot but think 

 that the view of Prof. Frank and Dr. Blass depends on too 

 one-sided a consideration of typical dicotyledonous anatomy. 

 . . . Our results as to the continuity of the various 

 phloem-systems in root and stem tend to give further ana- 

 tomical support to the theory of the conducting functions of 



