PLANT JUICES AND THEIR COMMERCIAL VALUES. 163 



milky jnice flows towards the incision. The lily family possesses long- 

 latex cells; magnolia, round. Madder and rhubarb have pigment cells 

 containing coloring matter, and some species of Acer have milk-sacs. 

 Latex consists of white granules suspended in a watery fluid. As 

 they are more or less numerous, the fluid is thicker or thinner. Some- 

 times it is yellowish, as in Clulidoniuui viajiis. In EiipJiorbea phos- 

 phor ea it is luminous. 



Balsam, gum, mucilage, or resin and mucilage mixed, when found 

 in plant juices, often cause the cell-walls to break down, so that the 

 cell spaces are also filled. Mucilage cells are always abnormally 

 large, and distended. 



Sugar is found abundantly in plant-sap, when pure, crystallized 

 and soluble, in the forms of grape sugar and cane sugar. The latter 

 occurs in sugar cane, sugar maple, beets, carrots, etc. Grape sugar 

 is found in such fruits as grapes, gooseberries, currants. Sugar forms 

 from 10 to 30"' of the juice of grapes; \2% of figs; 9 to lo;/ of sweet 

 cherries; 7 to \o''' of apples and pears; 2 to 5^ of plums; less than 2'fc of 

 peaches; 16 to 18' of sugar cane; 10 to 14" of sugar beets; 10 to w} of 

 sorghum ; 8"' of sugar maple .sap. Of this last product, belonging ex- 

 clusively to our own continent, a single tree of the Acer saccharinum 

 yields from two to four pounds of maple sugar annually, for forty 

 years, without being seriously injured. America produces about 

 30,000,000 pounds of maple sugar every year; Canada about half as 

 much. The tree does not thrive below latitude 38°. 



Beet-root sugar has been known more than one hundred years. 

 On January nth, 1799, Franz Karl Achard, director of the Royal 

 Prussian Academy of Science, submitted samples of this new article 

 to his sovereign, Frederick William III, who ordered that money be 

 supplied to Achard for continued experiments. Sugar then was a 

 rare luxury, purchasable by the rich only. To-day, 4.500,000 tons of 

 beet-root sugar are produced in Europe alone, along with 3,000,000 

 tons of cane sugar. Achard died poor, having refused a bribe of 

 200,000 thalers from the cane sugar people, who wanted him to pub- 

 lish a statement that he had made a mistake, and that beet-root would 

 not produce sugar. Cane sugar is boiled, crystalized, refined and cast 

 in moulds. The uncrystallized part becomes treaacle or molasses. 

 The beet-root sugar industry has been taken up with great success m 

 some of our states, especially Michigan. 



Certain acids are found in plant juices, as oxalic in almost all. 

 Fresh leaves of the sugar beet have 4:.' of acid. Tartaric acid occurs 

 free and combined with potassium in the juice of grapes and other 

 fruits. Malic acid imparts a sour taste to apples and kindred fruits. 



