. Essentials of biology presented in problems. Biology. THE STRUCTURE AND WORK OF THE STEM 107 in water. Wliite of egg, for example, is very slightly soluble, but can be rendered insoluble hy iieating it so that it coagulates. Insoluble proteids are digested within the plant; how and where is but slightly understood. In a plant, soluble proteids pass down the sieve tubes in the Inist and then nia>' be stored in the bast or medullary rays of the wood in an insoluble form, or they may pass into the fruit or seeds of a plant, and be stored there. What forces Water up the Stem. — We havo scon t
. Essentials of biology presented in problems. Biology. THE STRUCTURE AND WORK OF THE STEM 107 in water. Wliite of egg, for example, is very slightly soluble, but can be rendered insoluble hy iieating it so that it coagulates. Insoluble proteids are digested within the plant; how and where is but slightly understood. In a plant, soluble proteids pass down the sieve tubes in the Inist and then nia>' be stored in the bast or medullary rays of the wood in an insoluble form, or they may pass into the fruit or seeds of a plant, and be stored there. What forces Water up the Stem. — We havo scon that the process of osmosis is responsible for taking in soil wafer, and that the enormous aU- sorbing surface exposed by the root hairs makes possible the absorption of a largo amount of water. Frequently this is more than the weight of the plant in e\ ery twen(y- four hours. have been made which show that at certain times in the year this water is in some way forced up the tiny tubes of the stem. During the spring season, in young and rapidly growing trees, water has been proved to rise to a height of nearly ninety feet. The force that causes this rise of water i?t stems is known as root pressure. But root pressure alone cannot account for the rise of sap (water containing materials taken out of the soil) to a height of several hundred feet, as in the stems of the California big trees. Other forces must play a part here. One way in which the rise of water can be partly accounted for is in the fact that capil- lary attraction may help in part. If you place in a glass containing red or other colored fluid three or four tubes of differ- ent inside diameter, the fluid will be found to rise very much higher in the tubes having a smaller diameter. This is caused by capillarity or capil- lary attraction. When we consider that the tubes in the stem are oery much smaller than any we can make out of glass, it can be seen that water might rise in the stem to some height in
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1911
