148 A TEXT-BOOK OF BOTANY. 



Orchidacese, Piperacese, Fagacese, Aristolochiaceae, Polygonaceae, 

 Phytolaccace^, Nymphseacese, Ranunculacese, Menispermaceae, 

 Myristicacese, Lauraceae, Papaveraceae, Cruciferae, Rosaceae, Legu- 

 minosae, Geraniaceae, Rutaceae, Simarubaceae, Euphorbiaceae, 

 Celastrace^e, Sapindaceae, Rhamnaceae, Malvaceae, Thymelaeaceae, 

 Punicaceas, Myrtaceae, Umbelli ferae, Loganiaceae, Apocynaceae, 

 Convolvulaceae, Solanaceae, Scrophulariaceae, Gesneraceae, Rubia- 

 ceae, Caprifoliaceae, Valerianaceae, and Cucurbitaceae. 



Percentage of Starch in Plants. — The amount of starch 

 in economic plants, especially those used for food, is very high, 

 being, on an average, much greater than that of any other con- 

 stituent except water. The percentage of starch, calculated on 

 dry material, in a number of foods and spices is here given : Bar- 

 ley, 53.45 to 72.90; cardamom seed, 18.66 to 40.53; carrot, 0.87 

 to 0.92; chestnut, 37.31 to 47.93; chinquapin, 44.45; cinnamon, 

 10.44 to 65.72 ; cloves, 9.41 to 51.03 ; cocoa (cacao), 3.83 to 48.73 ; 

 corn, 36.72 to 77.54; ginger, 46.16 to 62.53; lentils, 45.37; mace, 

 26.77 to 56.11 ; millet, 56.70 to 74.40; nutmeg, 17.19 to 40.12; oak 

 acorns, 32.64; oats, 42.64 to 63.50; onion, 11.00 to 29.39; peas, 

 50.02 to 57.59; pepper, 28.15 to 64.92; pimenta, 16.56 to 59.28; 

 potatoes (sweet), 8 to 78.59; potatoes (white), 25.00 to 75.00; 

 rice, 74.80 to 84.41 ; rye, 51.15 to 74.08; wheat, 53.66 to 76.51. 



]\L\NUFACTURE OF Starch. — In the preparation of commer- 

 cial starches the object is to break the cells and separate the 

 starch grains, freeing the product from the other constituents of 

 the cell as much as possible. The preparation of potato starch 

 is exceedingly simple, as all that is necessary is to reduce the tubers 

 to a fine pulp, the starch grains being separated from the tissues 

 by means of a sieve. The water containing the starch is removed 

 to tanks, the separation of the starch being facilitated by the 

 addition of alum or sulphuric acid which coagulates the dissolved 

 protein substances. The starch is washed and dried over porous 

 bricks by exposure to air. It is then thoroughly dried in a hot 

 chamber, reduced to a powder, and sifted. One hundred pounds 

 of potatoes yield about 15 pounds of dry starch. It is said that 

 diseased tubers produce as good a quality of starch as the sound 

 tubers. 



In the preparation of the cereal starches the gluten interferes 



