ON PRUNING. 



153 



It is exceedingly difficult, however, to stop the 

 bleeding of a recent wound, and especially when 



serves the balance. Air is to be found in every portion of 

 earth ; and as it always contains a solution of the volatile parts 

 of animal and vegetable substances, we should be careful to 

 keep our stiff soils as open as possible to its influence. It passes, 

 both in its active and fixed state, into"the absorbent vessels of 

 the root, and, mixing with the juices of the plant, circulates 

 through every part. Dr. Hales, in his Statical Experiments 

 upon the Vine, discovered it ascending with the sap in the 

 bleeding season. 



" Having demonstrated that the motion of the sap depends 

 upon the influence of the air, and the power of absorption com- 

 mon to all capillary tubes, it naturally follows that it cannot 

 remain one moment at rest. The gradations from heat to cold, 

 and vice versa, are infinite, and sometimes desultory. So must 

 the motion of the sap. From the combinations of the nutritive 

 particles, a number of different fluids are prepared in the same 

 plant. Matter is the same in all ; but the modification of it 

 makes things sweet or sour, acrid or mild. 



" The universal juice of a plant is a limpid sub-acid liquor, 

 which flows plentifully from a wound made in a tree when the 

 sap is rising. The Birch and the Vine yield it in great abun- 

 dance. This liquor, as it moves through the innumerable small 

 vessels, becomes more and more concocted, and is the general 

 mass from which all the juices are derived. It may be called 

 the blood of the plant. By a certain modification it produces 

 high-flavoured oils, gums, honey, wax, turpentine, and even the 

 constituent parts of the plant itself. How this transmutation is 

 performed, remains, and perhaps ever will remain, unknown. 



' < I hope it will not be objected to me, that in this essay I 

 have been too minute. In the history of nature we cannot be 

 too particular. Every part of it demands our most serious at- 

 tention, and every part of it repays us for the labour we bestow. 

 The wings of the butterfly are painted by the same Almighty 



