256 COMPENDIUM OF GENERAL BOTANY. 



With the following enumeration of chemical comUnations and 

 mixtures of combinations only a few explanatory statements are 

 given; further detailed information in regard to theni has already 

 been given and may be referred to by the aid of the index. 



Carbohydrates, alhuminous substances, tannin, oils, fats, loax, 

 amides, 7'esin, coloring-substances^ ferments. 



Of the glucocides (whose formation and importance in the plant- 

 economy is still unknown) we ma}' mention araygdalin, salicin, digi- 

 tatin ; of the bitter extracts, lupulin and aloin. 



According to Pfeffer, and more especially to de Yeies, one 

 physiological activity of vegetable acids, that is, their salts, is that 

 they increase the hydrostatic pressure of the living cell by produc- 

 ing endosmotic action. 



The nitrogenous organic compounds of a basic character, namel}', 

 the alkaloids, must also be mentioned. They are very frequently 

 found in the laticiferous ducts of various plants. In the milky 

 juice of the poppy (opium-plant) are found thebaine, morphine, and 

 other alkaloids; in the bark of the Cinchona trees is found the alka- 

 loid quinine; strychnine is found in the seeds oiStrychnos; atropine, 

 daturine, hyoscynmine in the Solonacece, etc. These compounds 

 have a poisonous effect upon the animal organism, and may there- 

 fore serve the plant as a protection against the attacks of iinimals. 



Resins occur not only in conifers, but also in various exotic 

 plants. Incense is a resinous product of Bosivellia Carterii; 

 myrrh, of Coimniphora {Balsamodendron) Myrrha (Warming). 



According to Hoipe-Setler, cholesterin, which is widely dis- 

 tributed in seeds, is a secondary (catabolic) product of the albumi- 

 noids. 



Leaving chlorophyll out of consideration, there ai-e many other 

 coloring substances occurring in the vegetable kingdom. We will 

 refer only to those usually associated with chlorophyll. Red, 

 brown, brownish-yellow, and blue-green coloring-substances are met 

 with among various algse. Here also belong the coloring-substances 

 of flowers and fruits, of fungi, the coloring-substances in various 

 barks. Examples : the kino-red of Pterocarjms Mars^iplum 

 (FlDckiger) and the coloring-substances of other woods (ebony, etc.). 



In connection with the characteristic process of carbon-assimila- 

 tion it must be impressed upon the beginner in the study of j)lant- 

 physiology that there is a true respiration with liberation of CO^ and 

 assimilation of O, besides the usual api)ropriation of CO^ and libera- 



