RESIN CELLS I i i 



but only about half fills it longitudinally. This section is the most 

 useful for displaying the relations of the idioblasts to the adjacent 

 tracheids, inasmuch as the limits of the walls of the latter are 

 much more clearly defined. As seen in the tangential section, the 

 idioblasts fall into a single longitudinal series, which may not 

 embrace more than two or three members, but more commonly 

 there are upwards of twenty-one in a series. Not infrequently 

 the chain of crystals will be found to be interrupted for some 

 little distance, but the continuity of the idioblasts will then be 

 seen to be uninterrupted through the development of cylindrical 

 elements of uniform but smaller diameter and devoid of crystals, 

 from which it would appear that the lenticular or rounded form, 

 as determined by the particular plane of section, is not the normal 

 form of the cell, but that such special form results from the 

 growth of the crystal, which must have been deposited when the 

 tissue was in a formative stage of development. This is made 

 apparent in another very striking manner. In any tangential 

 exposure of such a series it may be seen that the terminal mem- 

 ber does not necessarily occupy all the space between the walls 

 of adjacent tracheids. There is thus developed an intercellular 

 space of variable dimensions, which may be quite small or may 

 be so extensive as to suggest that the crystals were formed in 

 such spaces and not in closed cells. Such spaces are obviously 

 not the result of that splitting which is ordinarily incident to the 

 growth of tissues, but they clearly arise as a secondary effect 

 incident to the development of the crystalline mass and the 

 pressure of this latter upon the surrounding parts. 



RESIN CELLS 



In a large proportion of the Conif erales the wood is character- 

 ized by the presence of more or less numerous wood-parenchyma 

 cells. These are always distinguished by their cylindrical form 

 and transverse terminations. They are invariably associated 

 with the production of resin, either as entering into the com- 

 position of resin passages or as isolated cells. It is this latter 



