ALKALOIDS. 119 



products of the vegetable kingdom, though they are not all 

 excreted. 



As we have already seen, the higher plants are marked by 

 the apparently small amount of their waste products and the 

 large amount of their formed material. The formed material 

 presents two very marked characteristics, which will, perhaps 

 be better understood if we designate them as formed material 

 and " fixed " material. Then we may class the formed material 

 as that which is elaborated and stored away for future use, 

 such as the starch, oil, etc., surrounding the germ in the 

 seeds, and in certain organs of the plant, and various other 

 products designed for future employment by the vital ener- 

 gies of the organism. The "fixed" material, on the other 

 hand, is such as is placed permanently beyond the vital ener- 

 gies of the organism. Some portions of the fixed material 

 may still be of use to the plant by the physical support it 

 gives to its organs; as lignin, which forms the stems and 

 branches of trees, and the bark, which serves them as a pro- 

 tection. They are not, however, of any further physiological 

 use to the plant after having once, or a few times, served as 

 conduits for the circulating fluids. 



Although waste products may be found in the fluids of the 

 plant, as in the blood of the animal, it is in this fixed material 

 that we find the bulk of these substances; and it is here that 

 the toxic principles are found in greatest abundance. Instead 

 of being excreted, thrown out to the outer world, they are 

 stored in the disused cells of the wood and bark, united with 

 other waste products in the form of insoluble compounds. 

 This fact seems to have prevented an early recognition of 

 their real nature. 



Sachs, in his text-book of botany, describes them as " de- 

 gradation products, which are no longer useful to the plant/' 

 and as " secondary products of metastasis." When we look 



