166 LEAF CANOPY AND PRUNING. [Jan., 



the drooping Oaks, Ashes, and Larches, and give them vigour to make a 

 Letter resistance to the baneful effects of the smoke. Tiie hopes of 

 maintaining green cover in South Yorkshire in the future seem to be 

 directed chiefly towards the Sycamore and Spanish Chestnut. The 

 Sycamore, too, when it springs up to some height, would require to be 

 underplanted with soil-sheltering wood. For, although isolated 

 Sycamores are provided with good dense heads of large leaves, yet, 

 growing together, they do not at an advanced stage sufticiently shade 

 the ground. 



Assuming the absence of any such precautionary underplanting, 

 some objections or dangers may be mentioned as peculiarly attaching 

 to open coverts with artificial pruning. The principal danger is that 

 already referred to — the exposure of the soil, endangering its continued 

 fertility, and entailing the loss of all those advantages enumerated at 

 the beginning of this paper. Although it is true that, other advan- 

 tages of site being equal, each tree in an open covert may make wood 

 rather faster than each tree in a close covert, yet too much of this- 

 wood is put on in the branches, whence the necessity for artificial 

 pruning. The shafts of trees in an open covert, unless they can be ' 

 corrected by pruning, taper very much ; whereas in close order, the 

 crowns and all the leaf power being set high in the canopy, the 

 shafts are proportionally thicker in their upper parts, and do not 

 diminish so rapidly in girth. In open coverts, too, the shafts 

 occasionally take a crooked form, since malformations due to frosts- 

 or other accidents in early youth are not corrected by the nursing or 

 competition of near neighbours. It is doubtful whether artificial 

 pruning can entirely eradicate crookedness of shaft. Open coverts 

 also show a good many cases of another defect — the forking of the 

 shaft. Artificial pruning can of course remove the competing leaders, 

 giving the tree one single axis or shaft ; but the resulting crookedness- 

 cannot so easily be corrected. Again, if each tree in an open covert 

 is liable to require pruning, it is not unlikely that, ^\dlere there are 

 many and extensive open coverts, there will be many more trees in 

 need of treatment than can possibly be attended to, without detriment 

 to other necessary forest operations. The difficulty is not lessened 

 by the consideration that each tree pruned will probably require 

 periodical pruning several times repeated during its life. This diffi- 

 culty of the application of labour, with the allied question of expense, 

 seems almost prohibitive of the multiplication of open coverts in a 

 large forest, or the employment of artificial pruning on a very 

 extensive scale. In France for a time great stress was laid on prun- 

 ing, ])ut it is said that the results were not altogether encouraging. 

 Pruning may perhaps be more feasible in the woods around the 

 residence of a wealthy proprietor, where labour may be available to 



