384 TREES : Chap. X. 



remarkable from announcing its maturity by " a spontaneous 

 and almost sudden dislocation/"' when deep cracks suddenly appear, 

 and the fruit falls to pieces: and this occurs with the wild C. momor- 

 dica. Finally, At. Xauclin well remarks that this 4i extraordinary 

 production of races and varieties by a single species and their 

 permanence when not interfered with by crossing, are phenomena 

 well calculated to cause reflection.''" 



Useful and Ornamental Trees. 



Trees deserve a passing notice on account of the numerous varieties 

 which they present, differing in then 1 precocity, in their maimer of 

 growth, their foliage, and bark. Thus of the common ash (Jfhtxin us 

 excelsior) the catalogue of Alessrs. Lawson of Edinburgh includes 

 twenty-one varieties, some of which differ much in their bark: 

 there is a yellow, a streaked reddish-white, a purple, a wart-barked 

 and a fungous-barked variety. 1 " Of hollies no less than eighty-four 

 varieties are grown alongside each other in Mr. Paul's nursery. 145 

 In the case of trees, all the recorded varieties, as far as I can find 

 out, have been suddenly produced by one single act of variation. 

 The length of time required to raise many generations, and the little 

 value set on the fanciful varieties, explains how it is that successive 

 modifications have not been accumulated by selection ; hence, 

 also, it follows that we do not here meet with sub-varieties subor- 

 dinate to varieties, and these again subordinate to higher groups. 

 On the Continent, however, where the forests are more carefully 

 attended to than in England, Alph. De Candolle 146 says that there 

 is not a forester who does not search for seeds from that variety 

 which he esteems the most valuable. 



Our useful trees have seldom been exposed to any great change 

 of conditions ; they have not been richly manured, and the English 

 kinds grow under their proper climate. Yet in examining extensive 

 beds of seedlings in nursery-gardens considerable differences may 

 be generally observed in them; and whilst touring in England 

 I have been surprised at the amount of difference in the appearance 

 of the same species in our hedgerow- and woods. But as plants 

 vary so much in a truly wild state, it would be difficult for even 

 a skilful botanist to pronounce whether, as I believe to be the 

 case, hedgerow trees vary more than those growing in a primeval 

 forest. Trees when planted by man in woods or hedges do not 

 grow where they would naturally be able to hold then* place 

 against a host of competitors, and are therefore exposed to conditions 

 not strictly natural : even this slight change would probably suffice 

 to cause seedlings raised from such trees to be variable. Whether 

 or not our half-wild English trees, as a general rule, are more 



144 Loudon's 'Arboretum et Fruti- 109/5. 

 cetuni,' vol. li. p. 1217. 14 °" 'Geograph. But.,' p. 1096, 



113 • Gardener's Chronicle,' 1866, p. 



