CHEMISTRY AND PHYSICS OF PLANTS. u3 
carnivorous plants, as the sundews (Drosera), fly-trap 
(Dionza), pitcher-plants (Sarracenia), etc., are in reality 
partially saprophytic, obtaining a considerable part of their 
food-materials from decaying animal matter. 
164, For convenience the various processes which take 
place’in the digestion of starch, the storing of reserve ma- 
terial, the use of other food-matters, etc., have all been in- 
cluded under one general term—Metastasis, or Metabolism. 
It has been made to include all chemical changes in the 
plant excepting assimilation (starch-making). Assimilation 
and metastasis thus include all chemical changes taking 
place in green plants. In all plants there is metastasis, 
while assimilation is present in those only which contain 
chlorophyll. 
165. Alkaloids and Acids——Among the most obscure of 
the metastatic changes are those which give rise to the 
alkaloids. These are compounds of carbon, hydrogen, ni- 
trogen, and generally oxygen, as follows: 
Nicotine (C1oHi,N:), found in tobacco. 
Cinchonia (C2oH24N20), found in Peruvian bark. 
Morphia (C,;HioNO;-+ H,0), found in the opium-poppy. 
Strychnia (Cs:H22N.0,), found in the seeds of Strychnos. 
Caffeine (Cs HioN,O.-+ H.0), found in coffee and tea. 
166. These and many others occur in plants in combina- 
tion with organic acids, such as malic acid (C,H,O,); tartaric 
acid (C,H,O,); citric acid (C,H,O,); oxalic acid (C,H,O,); 
tannic acid (C,,H,,0,,); quinic acid (C,H,,0,); meconic 
acid (C,H,O,). These acids are probably formed by the 
oxidation of some of the sugary or starchy substances in 
the plant, while the alkaloids with which they are combined 
appear to have some relation to the nitrogenous constitu- 
ents of the protoplasm. 
