200 PROCESS OF VEGETATION. 



soluble in water like gum or mucilage. Acid secretions 

 are well known to be very general in plants. The astrin- 

 gent principle would seem to be a sort of acid, of which 

 there are many different forms, or kinds, and among them 

 the tanning principle of the Oak, Willow,^ and others. To 

 the secretion of plants we owe the existence of sugar. In 

 tropical countries it is commonly obtained from the ex- 

 pressed juice of the sugar-cane, but the Maple of the North 

 yields it equally pure and scarcely less abundant. It exists 

 also in the roots of some, and in the esculent fruit of many 

 plants, communicating a sweet and usually an agreeable 

 taste. 



To the foregoing secretions of vegetables may be added 

 those on which their various colours depend. We can but 

 imperfectly account for the green so universal in their 

 herbage, but we may gratefully acknowledge the beneficence 

 of the Creator in clothing the earth with a colour the most 

 pleasing and the least fatiguing to our eyes. We may be 

 dazzled with the brilliancy of a flower-garden, but we repose 

 at leisure on the verdure of a grove or meadow. 



Questions. — 1. What is said of the whole vegetable body? 2. 

 What ere called the peculiar or secreted fluids of plants? 3. What i« 

 said of the sap ? 4. The Jlowing of the sap ? 5. What are some of 

 the most distinct secretions of vegetables ? 0. What is said of those se- 

 cretions on which the colours of vegetables depend ? 



LESSON 90. 



Process of Vegetation. 

 Incip'ient, just beginning. Suc'culent, juicy, moist. 

 When a seed is committed to the ground, it swells by the 

 moisture which its vessels soon absorb, and which, in con- 

 junction with some degree of heat, stimulates its vital prin- 

 ciple. Atmospherical air is also necessary to incipient 

 vegetation, for seeds in general will not grow under water, 

 except those of aquatic plants, nor under an exhausted re- 

 ceiver. Seeds buried in the ground to a greater depth than 

 is natural to them, do not vegetate, but they often retain the 

 power of vegetation for an unlimited period. Earth taken 

 from a considerable depth will, when exposed to the air, be 



