238 TEANSACTIONS OF THE HOETICULTUKAL 



ganic bodies. These vegetable organisms are consurnecl by animals 

 and elaborated into animal structure. 



In a primary sense, plants subsist upon tbe atmosphere and what 

 it contains; but they immediately derive much of their nourishment 

 from decaying organic substances that are incorporated with the soil. 

 But before such compounds can be appropriated by plants, they must 

 be resolved into their elementary state. They can be taken into the 

 organization of plants only in the condition of mineral substances, 

 and, even then, the most simple binary compound must be decom- 

 pounded before organization can begin. The processes of plant or- 

 ganization, and hence the health and longevity of the plants, depend 

 on a sufficient supply of sap, and its proper circulation through the 

 vital organism. Sap is essentially a watery fluid which the roots ab- 

 sorb from the earth, and holds in solution a small quantity of car- 

 bonic acid and ammonia, with other mineral constituents. In its 

 ascending course through the cells of the sap-wood, it meets with 

 and dissolves a portion of soluble cell-contents, and thus becomes 

 more and more dense as it approaches the buds, where it is appropri- 

 ated to the development of the leaf, in which it undergoes a further 

 elaboration, and returns upon the outside of the sap-wood to form a 

 new growth, and in this condition is called alburnum. 



The sap-wood is made up of elongated cells joined end to end, or 

 overlapping each other. At the growing season these cells are filled 

 with crude sap, the density of which increases from the spongioles 

 of the roots to the leaves. When first formed the cells are extremely 

 delicate and tender, and may continue their activity for a number of 

 years; but ultimately they become hardened by mineral deposits, and 

 become the hardwood of the tree, and completely lose their vital ac- 

 tivity. In a paper written for the Northern Society and published 

 in Transactions of 1884, I maintained that the cells of the plant or 

 tree constituted capillary tubes, and that the sap rose in the tree on 

 the principle of capillary attraction. A more thorough study of this 

 subject convinces me that the conclusions of that paper are incor- 

 rect. It has been ascertained that the sap circulates through the 

 vessels of the plant by means of a power equal to, or even greater 

 than that which drives the blood through the arteries of an elephant. 

 The celebrated Hales made a curious experiment, which proves that 

 there are forces other than mere capillary attraction that lift or force 

 the sap upward. Having fitted a long tube to the stem of a young 

 vine which he had severed, he saw the sap rise forty feet high. The 

 conclusion has been reached that the force with which the sap rises 

 in the vessels of the plant is nearly or quite equal to the pressure of 

 two atmospheres. Several eminent scientists, and among them 

 Shultz, of Berlin, believe that there are vital contractions of the tis- 

 sues of the plant, by which the sap is lifted with great power. 



Now, if there is a proper amount of moisture applied to the roots 

 to fill the vessels, holding in solution the inorganic elements neces- 



