DESTRUCTIVE METABOLISM 415 
Alkaloids. The alkaloids are numerous, and very important medi- 
cinally, as they are dangerous poisons or useful local stimulants, according 
to circumstances. A few, such as caffein from tea and coffee, theobromin 
from the seeds of cacao ("cocoa "), and the deadly muscarin from the 
poisonous mushroom (Amanita muscaria), are not related to the alka- 
loids proper, which are for the most part derivatives of pyridin and chin- 
olin. The true alkaloids are found in fungi and various seed plants, but 
are most common in certain families of dicotyls. For example, in the 
Papaveraceae, the oriental poppy alone yields more than twenty alka- 
loids, of which morphin, narcotin, and codein are best known ; in the 
Solanaceae, tobacco contains nicotin and others, and most of the other 
genera yield atropin and a number allied to it; a great number of the 
Apocynaceae have alkaloids in their latex, at least twenty different ones 
being known; in the Rubiaceae, the cinchonas and their allies produce 
more than thirty alkaloids, of which quinin and cinchonin are widely 
known ; in the Loganiaceae, seeds of Strychnos nux-vomica yield strych- 
nin and brucin, while another species yields several " curare " alkaloids ; 
and in the Erythroxylaceae, coca yields among others cocain, at once 
highly useful as a local anesthetic and utterly destructive to body and 
mind when used habitually. 
Coloring matters of flowers, fruits, barks, seeds, etc., are too numerous and 
varied to be discussed here. 
Ash. Mineral salts are present, sometimes amorphous, incrusting 
or incorporated in the cell walls, as is the case with silica; sometimes 
crystallized, as is the case with calcium oxalate. The ash of plants 
consists of the total mineral matter left as oxids when completely burned. 
Analysis shows that the amount and content of the ash varies much in 
the same plant in different situations, thus indicating that in part (and 
doubtless in large part) these materials are determined not by the 
" needs " of the plant but by the solutions which have opportunity to 
wander into it. Cultures under special conditions have shown that 
plants may be deprived of many of the chemical elements ordinarily 
found, and no evil effects follow; but the absence of others has obvious 
ill effects. Thus silica is an abundant material in the cell walls of the 
epidermis of most cereals; yet corn has been cultivated through four 
generations with practically no silica. 
Necessary elements. A list of the elements that have been found in 
the ash of one plant or another would be almost a list of the commoner 
