TEEES FOE WATEE CATCHMENT AEEAS 121 



accelerated by the discovery, in the early part of the nine- 

 teenth century, of the trees of the Pacific Coast region of 

 North America, where, in a climate absolutely similar to 

 our own, the highest and most valuable type of coniferous 

 forest on the planet has been evolved. The Douglas fir, 

 Sitka spruce, Abies nohilis and grandis, Thuya gigantea, 

 Fimis insignis, and Cupressus macrocarpa are perhaps the 

 most important trees from this region. From Asia we have 

 introduced the Japanese larch. 



There are numerous other trees, which are occasionally 

 used in our plantations, but scarcely any promise to be of 

 real value. In fact, the pursuit of new species is over as 

 regards commercial forestry. We have all the wild species 

 that we need. It is different with regard to trees of hybrid 

 origin. Eemarkable fastness of growth, far surpassing that 

 of wild species of the same genus, is shown by certain 

 hybrids of the first generation, or so-called ' first crosses.' 

 Amongst these may be mentioned black Italian poplar, 

 cricket-bat willow, and London plane, all hybrid trees which 

 originated as chance seedlings. Fast-growing hybrids of 

 trees like ash, walnut, oak, etc., if they could be produced 

 by artificial cross-pollination, would be invaluable ; and 

 efforts to make such hybrids have been attempted. One of 

 the most interesting of these artificially made trees is a new 

 hybrid poplar, Popuhis generosa, produced at Kew in 1912 

 (see Gardeners' Chronicle, Ivi. p. 257 (1914)). As to the 

 quality of the wood of these hybrid trees, I may quote from 

 my article on " The Artificial Production of Vigorous 

 Trees," in Journ. Dept. of Agriculture, Ireland, xv. p. 42 

 (1915): 



" It is a popular belief that fast-grown timber is neces- 

 sarily soft and comparatively worthless. This is a fact in 

 most conifers ; but in one class of broad-leaf trees, the wood 

 of which is characterised by large pores in the inner part of 

 the annual ring, the contrary is true, as the faster the timber 

 of these trees is grown the stronger and denser it becomes. 

 This class includes oak, ash, chestnut, hickory, and walnut, 

 the species, in fact, that par excellence produce the most 



