308 



A NOTE ON VINE BORDERS. 



leedi require nir for their growth, it is be- 

 lieved Dr, Stevens will not deny; nor 

 should I have thought it necessary to state 

 the above proofs, except for the analogy 

 which germination bears to the growth of 

 plants. The question is therefore merely, 

 whether the healthy vegetation of plants 

 require the presence of atmospheric air at 

 iheir roots* 



It is well known to Pr. S. that* under the 

 common pressure of the atmosphere, no air- 

 pump has been so perfect as to produce a 

 complete vacuum; and also, that such is 

 the permeating subtlety of this elastic fluid, 

 that the cells of all porous substances which 

 have been examined are found to contain 

 more or less air. 



The depth to which air penetrates the 

 ground, it is true, must depend on the na- 

 ture of the soil. Adhesive clay, pressed 

 down and kept moist, would admit but a 

 small quantity when compared with the 

 more porous sand or gravel ; but of what- 

 ever materials the soil may be composed, 

 there is no doubt that the air finds its way 

 through it, to a depth equal to that of the 

 roots of any healthy Vegetable of whatever 

 kind. 



The following example will show how 

 small is the obstruction of common garden 

 soil to the permeation of the atmosphere; 

 A well is situated four rods from the pump ; 

 the water being drawn by means of a tube 

 three feet under ground, and descending 

 twenty-seven feet into the well. On the 

 top of the brick surrounding the well is laid 

 a flagging stone, entire, and say four inches 

 thick, and four feet square ; and on this 

 a quantity of earth sufficient to p.oduce 

 grass, so that no signs of the well are ap* 

 parent. And yet so free is the access of 



the atmosphere to the Water, that the fluid 

 is delivered by a common iron pump, (which 

 demands atmospheric pressure,) situated 

 four rods from its source, and thirty feet 

 above its surface* 



This example is stated to show that, al* 

 though " trees grow perfectly well in cities, 

 with their roots under stone flagging," yet 

 this fact by no means proves that the air 

 is not always in contact with their roots. 

 On the Contrary, it is Well known that if 

 seeds are buried in the earth, to the depth 

 of several feet below the surface, so that 

 they are entirely beyond the reach of the 

 oxygen of the atmosphere, they will never 

 germinate, but may still retain their vitality, 

 even for centuries ; hence it is common for 

 alluvial soils, from deep excavations, to pro- 

 duce plants, when exposed to the vivifying 

 influence of the atmosphere. 



We know, also, that if the roots of grow- 

 ing trees be covered with several feet of 

 soil, that they certainly perish in a year or 

 two. That this does not arise from the 

 want of heat, appears, from the fact that 

 clay, of an equal depth, is more destructive 

 than sand,— the latter being most permea* 

 ble to the air ; and that the destruction is 

 not caused by the pressure, will appear 

 when it is known that the same, or even 

 double the weight of broken stones, would 

 not in the least affect either the growth or 

 the bearing of the tree. 



We might bring many other facts, to 

 show the absolute necessity of common air 

 to the roots of plants for healthy vegetation. 

 But not to protract this letter, I will only 

 add, that I remain the humble servant of 

 both Dr. Stevens and the Editor. 



J. L. Comstock. 



Hartford, December 10, 1849, 



