ANATOMY OF THE GYMNOSPERMS 



alcohol, and completely in the case of potassium hydrate. In the 

 ether reaction there did appear to be a certain diminution in 

 volume, apparently through solution, when the reagent was first 

 applied, but after that there was no further alteration. The 

 application of alcohol, both in the hot and in the cold, showed 

 that while the resin contained in the medullary rays was all 

 dissolved, the plates were only partially affected. The reaction 

 of the reagent was chiefly manifested in the development of 

 strong curvature, often accompanied by fracture (fig. 4, r.p}. 

 This was evidently due to an increase in volume as the first tend- 

 ency toward solution, and it gave the first definite evidence that 

 the plates could not be of a cellulose character. Beyond this 



no further change was brought 

 about, even after several weeks 

 of action. The potassium hy- 

 r p r p drate gave the most positive 



results. At first there was no 

 apparent change, but after 

 an interval of about ten days 

 or two weeks the plates were 

 found to have completely dis- 

 FIG. 7. DAMMARA AUSTRALIS. Radial appeared, leaving a perfectly 



section showing the origin of the resin i , i ., n , 



clear channel in the cell cavity. 



plates (r.p.). x 225 J 



A further proof of the resinous 



character of these plates is to be found in the ruptures which 

 they not infrequently exhibit (fig. 4, r.p.}, and in the various 

 developmental stages which may be observed without difficulty 

 (fig. 7). These show that the resin gathers locally upon the 

 inner face of the tracheid wall, and as its volume increases it 

 projects from all sides toward the center, where it coalesces 

 to form a continuous and imperforate septum. The facts thus 

 obtained prove most conclusively that the plates are not cellu- 

 lose, and although immersion in concentrated cupric acetate for 

 eight weeks failed to develop the characteristic reaction, they 

 point to the idea that the plates are probably resinous. The con- 

 clusion is probably justifiable that they consist of gum dammar, 



