182 I). P. Penhatloiv — Tendril Movements in 



with a strong, marginal contraction, which is found to be devel- 

 oped in the collenchj^ma itself. Longitudinal sections show a 

 strong curvature with the concavity on the side along which 

 the collenchyma runs, clearly demonstrating the strong tension 

 of this tissue. We are also inclined to believe that the cutting, 

 as all other irritation, causes a certain loss of water from the 

 tissue within the area of irritation, and thus through con- 

 densation, a contraction and further increase of tension. This 

 is essentially the view adopted by Sachs,* and it certainly 

 appears justified. We must therefore not only regard the 

 collenchyma as influencing all the movements dependent 

 upon growth, but it must also be considered as that tissue 

 which chiefly determines all movements caused by mechanical 

 irritation, a view which is amply supported by its presence 

 in the tendrils of Vilis, Sicyos, Ampelopsis • and other vines, 

 and the relation which it there bears to the movements of these 

 tendrils. 



The unmodified fundamental tissue, of large, rounded cells 

 filled with protoplasm, is that in which the most rapid and con- 

 tinued increase takes place. As the central or pith region early 

 loses its vigor and often shrinks away radially, that part lying 

 externally to the wood zone and internal^ to the collenchyma 

 is obviously the general region of this tissue which serves to 

 retain the power of growth for the longest period, and of this, 

 we find the vibrogen bands to not only represent the most 

 active growth from the outset, but they retain it up to the 

 latest period. Even after the tendril has become well fixed in 

 a permanent spiral, the vibrogen will be found to contain an 

 abundance of chlorophyll and protoplasm, and thus to essen- 

 tially retain its power of extension, although then held in abey- 

 ance by the permanant character of the fibrous tissues. We 

 must then conclude that the negative tension is most strongly 

 developed in the parenchyma as a whole, and in the vibrogen in 

 particular, while the positive tension is developed in all the 

 fibrous elements, particularly in the collenchyma during the 

 earlier periods of activity, and in the wood cells towards the close 

 of the active period. 



The collenchyma also bears an important relation to the 

 other tissues in its hygroscopic powers. It is a tissue which is 

 capable of the greatest variation of density through absorption 

 and liberation of water, and whenever such a change is induced 

 by any means, this tissue must become of primary importance 

 in determining secondary movements in the tendril to which it 

 belongs. From the information we have collected, not only 

 with reference to this but to other tendrils as well, we feel toler- 

 ably safe in the view, that, in all cases of sensitive tendrils, the 



* Text Book, p. 869. 



