ROOTS. 17 



1st. The absorption of nutritive matter: 



2d. The transportation of the nutritive liquid or sap to the 

 organs of respiration. 



3d. The process of respiration and elaboration (or prepa- 

 ration) of the nutritive juices in the interior of the respiratory 

 organs. 



4th. The transportation of the sap thus elaborated to different 

 parts of the plant, and the deposition or assimilation of its ele- 

 ments in its various parts. 



5th. The secretion of peculiar juices effected by special 

 organs. 



2. The roots of plants absorb the nutritive matter necessary 

 for the maintenance of vegetable life, and the liquids, thus in- 

 troduced into the body of the vegetable, constitute what is called 

 the ascending sap. This sap rises through the stem by means 

 of particular canals, and in this manner reaches the leaves and 

 other green parts of plants; there it is modified by the effects of 

 transpiration and of respiration, and after having been thus pre- 

 pared, the sap descends, following a new route, and is distributed 

 to those parts for the growth of which it is destined. 



We will study successively these phenomena, and the organs 

 which are the seat of them, both in vascular and cellular plants. 



OF THE ABSORPTION AND ASCENT OF SAP. 



3. The absorption of nutritive matters is principally effected by 

 the extremity of the roots, and by passing through these organs 

 and mounting along the stem, they reach the leaves, in the sub- 

 stance of which the alimentary juice is rendered fit for the nutri- 

 tion of the plant. These two phenomena, the absorption and 

 ascent of the sap, are very intimately united ; and in order to un- 

 derstand them, we must, in the first place, study the structure of 

 .the two portions of the plant which are the seat of them, namely, 

 the roots and stem. 



OF THE ROOT OR DESCENDING AXIS (RADIX). 



4. We give the name of root to that inferior portion of plants 

 which serves to fix them in the soil, and which, by its growth, 

 increases in length in an opposite direction to the stem. 



5. With the exception of some plants that live under water, or 

 float upon its surface, all vegetables are provided with roots, 



2. What is ascending sap ? -What becomes of this ascending sap? 



3. Through what part of a plant is matter chiefly conveyed for its nour- 

 ishment. 



4. What is meant by the root of the plant? 



5. Are all plants provided with roots? Where are the roots usually 

 found ? What are adventitious roots ? 



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