(io 4 ) 



large collection, generously donated by E. Merck & Com- 

 pany, of New York, and valued at several thousand dollars, 

 contains all of the more important proximate principles of 

 plants, some of them being worth as much as five or ten 

 dollars per grain. 



Starches. Case j6. — Starch is largely formed by most 

 plants, as a reserve food supply, from the water taken in 

 through the roots and the carbonic acid gas inhaled from 

 the atmosphere; the chemical combination is effected by 

 the sun's energy, directed by the green coloring matter 

 (chlorophyl). Starch is mostly found in the form of 

 granules, sometimes in small rods, and is easily converted 

 by the plant, or artificially, into glucose, in which form 

 the plant consumes it. In darkness the plant consumes 

 starch previously formed in daylight. Starch is insoluble 

 in water and can therefore be easily washed out from ground 

 plant tissue. The forms of the starch grains are so con- 

 stant and characteristic in each plant that they afford an 

 excellent method of identifying the latter, even in powder. 

 Starch, as in the case of many other substances, exists in 

 and is consequently derived from the several organs of 

 various plants, for example, the roots of the cassava plant 

 furnish the cassava flour and tapioca, while those of coontie 

 yield coontie flour or Florida arrowroot, which is quite 

 similar to sago, and those of the sweet-potato plant furnish 

 sweet-potato flour. The rootstocks of the common potato 

 plant abound in potato flour, while those of the arrowroot 

 plant yield arrowroot flour. The stems of some of the 

 sago palms and those of some of the true palms are the 

 sources of sago flour. The fruits, both dry and fleshy, of a 

 great variety of plants, contain starch; for example, those 

 of the several grains, wheat, rye, and corn; while those of 

 the banana yield the less common banana flour. The 

 seeds of some plants are used as a source of starch. 



Sugars. Cases 77 and 78. — Sugars are formed by plants 

 at a stage in the manufacture of carbohydrate foods, and 

 again when the carbohydrate is used by the plant as food, 



