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ROYAL SOCIETY OF CANADA 



so that the internal space which is viltimately developed does not reach, 

 quite to the ends, but stops some distance short (fig. 1). This typical 

 structure, however, does not seem to apply throughout, since a series of 

 sections discloses local variations of a more or less marked character. 

 Thus in figure 8 it will be seen that an area of parenchyma of circular 

 form, has been cut ;off from the princijDal mass of structure and has 

 formed cork all about it. Such nodal areas are sometimes duplicated by 

 smaller lones (fig. 9), but whether there are one or two, the same de- 

 velopment occurs at opposite ends of the same! section. Another varia- 

 tion also appears locally, in the development of radiating zones of more 

 dense structure (fig. 8). Whenever such zones appear, they lie between 

 the nodal areas of parenchyma and the principal mass of tissue, and 



Fig 6. x '2.Ô0. 



thence extending outwardly, they curve upward toward the narrower end 

 of the section, at the same time broadening out in a fan-shaped manner. 

 Upon a careful analysis of this region, it is found to be composed of a very 

 compact and modified cork tissue which forms a perfectly continuous 

 structure without absciss layers. The first suggestion arising from this 

 observation is, that such regions are designed to furnish a necessary de- 

 gree of cohesion between the various layers of cork which would other- 

 wise become separated at an early period of development, whereby the 

 integrity of the structure as a whole would be seriously jeopardized. 

 Such indeed may be the case, but it does not serve to explain the origin 

 of such localized variations in structure. Upon a closer scrutiny of the 

 various parts, it will be observed that the following facts may be 

 noted : — 



1. The fan-shaped tissue has its greatest expansion in the outer 

 layers of cork. 



