No. 133.] 441 



again through the leaves, stem, and bark, with the new supply of 

 liquid imbibed from the earth. This sap is supposed to irritate 

 the capillary tubes, which are almost as fine as a hair, causing 

 them to contract an'd expand, thus expelling the liquid to all 

 parts of the plant. I imagine that electricity has more to do with 

 the ascent and descent of sap than any other agent. The sub- 

 stances made use of for green manuring, are buckwheat, rye, red 

 clover, old grass, corn, seaweed, &c. Dry vegetable substances, 

 rye and wheat chaff, rye and wheat straw, leaves and other simi- 

 lar matters; decayed vegetable matter, much mixed with dried 

 farm yard manure ; peat with lime, and salt, and tanner's bark ; 

 soot, charcoal, dust, blood, flesh, wool, rags, bones, hair, horns, 

 refuse from sugar houses, fish, pigeon, and fowls excrement, 

 guano, of man, the sheep, pig, horse and cow. All these matters 

 must become liquid before they can enter the roots of vegetables. 

 Plants perspire very freely when the weather is dry, and diminish 

 the quantity when it is humid. A sun flower weighing three 

 pounds, has been known to perspire 22 ounces in 24 hours, where 

 a man generally perspires about 31 ounces in the same length of 

 time. If this perspiration of vegetables is checked in any way, 

 they fade at once For your amusement, place green leaves in 

 water directly under the rays of the sun, and you will observe 

 air bubbles collecting on them, which will finally rise to the sur- 

 face and burst ; if collected in a bottle, you will find the gas pure 

 oxygen. Thus the sun matures fruits, by expelling oxygen ; he 

 changes them from sour to a mild sweet substance. Aquatic 

 plants purify the air by absorbing hydrogen gas and yielding 

 oxygen. The willow likewise enjoys this power in a remarkable 

 degree, as is shown by its rapid growth in marshy places where 

 this gas abounds. The air contained in the bladders of marine 

 plants is much purer than common air ; in situations wiiere they 

 abound we are indebted for the purity of the atmosphere in the 

 day time and impurity at night. If lights were burned at night 

 in presence of the plants, they would continue to produce pure 

 air. 



All plants have organic elements which they obtain from the 

 earth and air. Carbon is one of these, and must enter either in a 



