246 ROYAL SOCIETY OF CANADA 



and transpiratory organs, indicates that the development could not have 

 been greatly prolonged, and that not only was the entire length com- 

 pleted within a short time, but that the formation of the cork tissue 

 must likewise have been completed within a correspondingly brief in- 

 terval. If we seek elsewhere, examples confirmatory of such develop- 

 ment, it is very difficult indeed to find them in this latitude. It is true 

 that in tropical latitudes numerous examples of rhizophores and aerial 

 roots may be found, and these offer general parallels" in development. 

 But such serial organs require for their growth, a humid atmosphere of 

 relatively high temperature, and this rarely obtains — certainly not for 

 any prolonged period — in a northern latitude such as that of New 

 Brunswick; and even if, under exceptional circumstances such a com- 

 bination were to occur in a moist woodland, it would still be difficult to 

 consider it sufficient in itself, to induce the development of such a struc- 

 ture without the primary assfstance of some special stimulus such as 

 would arise through the presence of a definite lesion of some sort. For 

 we are now dealing with an abnormal growth, and not Avith a normal 

 development of lateral organs such as would be presented by aerial roots 

 and rhizophores. And here we are faced with a mechanical difficulty of 

 some importance. The bark of the white birch is enclosed in a definite 

 periderm of considerable thickness composed of a large number of super- 

 imposed layers oi cork. It would require considerable force to rupture 

 such an investing membrane, and we should rather expect, as occurs 

 usually in such cases, for the hypertrophy to respond to the pressure and 

 give rise to a tuuiour of more or less spherical form, situated beneath the 

 outer bark. But in this case the very remarkable form of the outgrowth 

 itself may assist us to a correct interpretation of the facts. The " rope " — 

 so-called because of its attenuated form, but without implying any torsion 

 of its structure — has been found to present the form of a narrow ellipse 

 in transverse section. This can have but one meaning with respect to 

 the position which the rope occupied on the tree. It would be mani- 

 festly impossible for it to grow with its major axis in a vertical plane, 

 for even if it emerged from the bark in that position, the effect of its 

 own weight would soon develop a torsion which would speedily bring the 

 major axis into a horizontal jiosition, and this, we may as- 

 sume, was its real position from the very outset of its de- 

 velopment. Now it is to be observed that while the thickness of 

 the rope may very readily have been the result of subsequent expansion, 

 the breadth and more particularly the form, are in direct conformity 

 with the length and the general shape of a lenticel which always occupies 

 a horizontal position in the white birch. Such a lenticel would form a 

 very natural point of emergence as a region of least resistance for a hy- 



