130 ON THE ACTION OF WATER 



Emily. But how can the wood absorb water if it does 

 not pass through the bark ? 



Mrs. B. The wood absorbs water by the internal ves- 

 sels. If the trunk of a felled tree lie on the ground in a 

 damp spot, with the roots and branches cut away, so as 

 to leave the vessels exposed at both ends, it will absorb 

 .so much water as frequently to make it sprout small 

 branches and leaves. 



Emily. I recollect seeing an instance of this in Kensing- 

 ton Gardens : the log was lying in a dell, partly immersed 

 in water, and the whole of it was sprouting with verdure. 



Mrs. B. Thirdly, water conveys air into plants ; and 

 the more it is impregnated with air, whether atmospheric 

 or carbonic acid, the better it is adapted to vegetation. 

 Thus the water of large rivers which flow rapidly, and pass 

 over a great extent of country exposed to the influence 

 of the atmosphere, is much more favorable to vegetation 

 than that of small rivulets, which have not been a sufficient 

 length of time in contact with the atmosphere to become 

 impregnated with air : yet this latter is preferable to the 

 water of a lake, which has no current ; for it requires mo- 

 tion, and pretty strong motion, to mix water and air to- 

 gether in the quantity which is required by plants. . Large 

 lakes, such as that of Geneva, it is true, are considerably 

 agitated by the wind : the waves then swallow up a cer- 

 tain quantity of air ; but when tranquil it contains much 

 less than river water. 



Caroline. Yet is not the water of ponds preferred to 

 that of rivers for watering plants, although it is so tran- 

 quil as frequently to become stagnant, and to be covered 

 with a green slime, which shows that it can have been 

 little agitated by the wind ? 



Mrs. B. This green scum is a vegetable production, 

 affording food to numerous swarms of the insect tribe, 

 flies, worms, snails, &,c. In a short space of time this 

 little ephemeral population, as well as the vegetables 

 which nourished it, perish, and putrefaction succeeds, as 



723. How does wood absorb water if it does not pass through the 

 bark 1 ? 724. What illustration of this does Mrs. B. give 1 ? 725. 

 And what one does Emily give 1 ? 726. What is the third way in 

 which water operates on plants'! 727. Why is the water of a large 

 river more favorable to vegetation than that of small rivulets'? 728. 

 And why is the water of small rivulets more favorable to it, than the wa- 

 ter of lakes'? 729. What is said of large lakes, as that of Geneva, 

 in relation to this matter'? 



