PLANT JUICES AND THEIR COMMERCIAL VALUES. 

 By Mrs. Caroline A . Crccvey. 



EVERY time we place cut flowers in a vase partly filled with 

 water we show our faith, if not our knowledge. So long- as 

 water runs through the stems and branches, replacing evapora- 

 tion from the leaves so long our plant will hold its freshness. 

 When from degeneracy of the cell walls, the supply to the cut stems 

 becomes less than the amount given off, our flower decays. Growing 

 plants take up water principally from the soil by means of their more 

 or less intricate system of roots and rootlets; also from the air through 

 open cells in the leaves. The crude sap ascends and descends, making 

 a circulation similar to that of blood in animals. In the higher plants, 

 cells for conducting water are especially differentiated, being usually 

 long and narrow in shape. Even in mosses and other cellular plants, 

 the water-carrying cells are long and duct-like. The cell walls are 

 permeable, and water passes easily through them, seldom, at least in 

 the daytime, remaining in a state of suspense. What causes water to 

 ascend, contrary to the laws of gravitation, has not been wholly ex- 

 plained. There are many theories. Capillary attraction accounts in 

 part for this phenomenon, but not for all of it. Boehm says it is due 

 to "phenomenon of filtration, caused by differences of pressure in 

 contiguous cells." Since there is not time to discuss this subject, let 

 us say in unscientific language : "Water rises in a plant partly by 

 capillary attraction, partly as water is raised in a pump, by a sort of 

 suction. The constant evaporation from the stomata of the leaves 

 sends a call through the succession of cells, down to the roots for more 

 to fill the tiny vacuums." By absorption of water through the leaves 

 alone, moist atmospheres will keep a plant fresh for a long time, even 

 in a dry soil. Fleshy plants like the cacti, which evaporate almost no 

 water, are especially fitted for life in arid, desert regions. 



It would be interesting to recall some experiments which have 

 been made in order to test the amount of pressure exercised by 

 ascending sap. This varies under different conditions and at different 

 hours of the day and night. For example, it has been demonstrated 

 that at 6 a. m., April 21st, the suction in a tree was sufficient to 

 raise a column of water 25.95 feet, while two hours later, after the 

 sun had fully risen, the pressure sustained a column of water forty- 

 four feet in height. The Passion flower contains a very large quan- 

 tity of water. Passiflora actina, growing in the Kew Gardens, when 

 cut, yielded a gallon of pure water in one minute. Musset reports 



