166 FOKESTS, WOODS, AND TREES 



planted 15 to 20 feet apart, in single or double lines, 

 around small fields. The crop of grass or hay is not per- 

 ceptibly diminished ; and a large volume of timber of 

 considerable size and value results from the growth of the 

 trees thus isolated. 



The wood of the black Italian poplar is tough and light, 

 resisting wear well. It is in demand for special purposes, 

 as for brake and slipper blocks, and for polishing plate-glass 

 in the course of its manufacture. It is used for beds of 

 waggons and carts and for packing-cases. Being uninflam- 

 mable to a considerable degree, it is suitable for flooring in 

 factories and other buildings. It is now utilised in the 

 making of plywood. When well seasoned it is capable of a 

 fine polish, and is useful for making cheap furniture. 



There are several other hybrid poplars which have not 

 yet been extensively planted in this country. The best 

 of these are : (1) Eucalyptus poplar {Populus regenerata, 

 Fig. 32), similar in foliage to the black Italian poplar, but 

 bearing female flowers. (2) Populus E^tgenei, narrower in 

 the crown than black Italian poplar ; it makes rapid growth 

 on sandy soil at Kew (Fig. 33). (3) Populus rohusta, with 

 a very narrow crown, thriving at Glasnevin. This promises 

 to resist wind better than the other poplars. The history 

 and description of these poplars is fully given by the writer 

 in GardcTiers Chronicle, Iv. pp. 1, 46, 66 (1914), and in 

 Trans. Roy. Scot. Arhor. Soc. xxx. pp. 14-27 (1916). 



2. Grey poplar {Populus canesce7is). This tree is not so 

 fast in growth as black Italian poplar ; but it produces a 

 better quality of timber, light in weight and very strong, 

 useful for carriage building. This poplar is very hardy and 

 may be planted along water courses and in frosty meadows. 

 It is not suitable for plantations, but makes a splendid 

 standard in coppice on stiff clay soil. White poplar 

 (Populus alha) is more sensitive to wind and frost than grey 

 poplar, and does not attain so large a size in England. In 

 most situations grey poplar is to be preferred as being the 

 more vigorous tree. 



3. As^en (Popidus tremula). The aspen is a native tree 



