290 TAYLOR-ON THE PRODUCTION OF 



irregular mass of cells, while on the other hand there was sometimes 

 formed a distinct cambium. This cambium often split oflf cells like 

 the most typical cork-cambium (Plate LXXVIII, Fig. 28). This is 

 a different condition from that so often seen, where the outer layer of 

 the cortex gives rise to the cork cambium. It was only found around 

 wounds of injection or fissures in the epidermis resulting from mechanical 

 injuries. 



The inner cortex, which was parenchymatous, showed in all species 

 a ready ability to prohferate. The causes which operated on the outer 

 cortex were effective here also. The cork-like formation was present as 

 in the outer cortex, both often taking part in the same reaction. It is 

 improbable that much tissue could be laid down from the proliferation of 

 these cortical cells. 



The scleroid patches, when present, took no part in the reaction. 

 No new scleroid tissue was produced. 



The most prominent and interesting tissue production was from the 

 innermost cortical layers. This formed the extra-fascicular bundles 

 of the type mentioned by Schilberszky (4). When some great disturb- 

 ance of the function of the stem occurred, such as the killing of a large 

 part of the internode by the toxic action of the injection, the stem re- 

 sponded by the formation of extra-fascicular bundles. When the pith 

 was killed, (and possibly also the xylem affected,) these bundles were 

 often produced. In the former case as active a reaction would probably 

 have been produced by the simple operation of removing a part of the 

 internode, thus exposing the interior to drying. This is practically 

 what Schilberszky did. The xylem produced was quite abnormal in 

 appearance, the small pitted vessels being much distorted and displaced 

 from their normal orientation. They became well lignified, however, 

 and were quite unmistakable. These were produced in Polygonum 

 alone, for only there were the solutions sufficiently strong to cause the 

 necessary tissue destruction. The production of these bundles was 

 limited to the neighborhood of the wounded region (Plate LXXVIII 

 Figs. 25, 26, 27). 



Schilberszky (4) describes the formation of both phloem and xylem. 

 In the writer's preparations there was no well-defined phloem shown. 

 Outside the xylem, and dipping into it in places, there was a soft tissue 

 which took the Methyl Green stain readily, but it was not possible to 

 difi'erentiate it into a meristematic and a matured layer. 



The Phloem is the next tissue to be considered. Generally it showed 

 no response to the injections, but in at least one case of Polygonum 



