(2 9 ) 



active tissue that constitutes the "sap-wood." From such 

 trunks the sap-wood is therefore usually trimmed off before 

 the logs are sent to market. In most cases, dye-stuffs 

 show some coloration to indicate the presence of their 

 coloring matters, although the color thus seen may be 

 quite a different one from that which the material will 

 produce when in practical use. Sometimes no coloration 

 is to be seen in the dye-stuff, some chemical treatment 

 being necessary to develop it. 



Although the use of anilin or coal-tar colors has very 

 largely replaced that of vegetable dyes, there is still a vast 

 use of the latter. But for the introduction of the former, 

 it is difficult to see how the demand for colors could have 

 been supplied under modern conditions. 



Tanning Materials. Cases 37 to 38. — The tanning 

 materials are also very important from an economic stand- 

 point. They depend for their value chiefly upon the 

 tannic acid that they contain, but that other constituents 

 contribute is clear from the fact that a substance containing 

 less tannin may be more valuable than one containing a 

 larger percentage. The tannin cures and toughens the 

 skin, but other effects are required to produce the best 

 quality of leather, especially that of "filling" the minute 

 cavities. For this purpose white-oak bark seems to be 

 preeminent and this continues to be the most valued tanning 

 substance. It has become scarce and costly, and "oak 

 leather "now brings the highest prices. The tannins are 

 represented by saw-palmetto, mangrove, pine, hemlock, 

 and sumac. The crude materials of the mangrove and 

 the saw-palmetto are accompanied by their fluid extracts, 

 which contain the tannic acid, and also by the spent 

 material or refuse which remains after the extract has been 

 made. This latter material may be used for other purposes. 



Fodder Plants. Cases 39 and 40. — Following the spices 

 are fodder plants, which are shown as sheaves. Fodders 

 are derived chiefly from plants of the grass and bean fami- 

 lies. Illustrations of the former are the varieties of hay 



