386 TEEES. Chap. X 



which generally transmit their character by seed. 156 The occur- 

 rence, in trees belonging to widely different orders, of weeping 

 and fastigate varieties, and of trees bearing deeply cut, variegated, 

 and purple leaves, shows that these deviations of structure must 

 result from some very general physiological laws. 



Differences in general appearance and foliage, not more strongly 

 marked than those above indicated, have led good observers to 

 rank as distinct species certain forms which are now known to be 

 mere varieties. Thus, a plane-tree long cultivated in England 

 was considered by almost every one as a North American species : 

 but is now ascertained by old records, as I am informed by Dr. 

 Hooker, to be a variety. So, again, the Thuja penchda or filiform) s 

 was ranked by such good observers as Lambert, Wallich, and 

 others, as a true species ; but it is now known that the original 

 plants, five in number, suddenly appeared in a bed of seedlings, 

 raised at Mr. Loddige's nursery, from T. orien talis; and Dr. Hooker 

 has adduced excellent evidence that at Turin seeds of T. pendula 

 have reproduced the parent form. T. oriental is. 15 ' 



Every one must have noticed how certain individual trees regu- 

 larly put forth and shed their leaves earlier or later than others 

 of the same species. There is a famous horse-chesnut in the 

 Tuileries which is named from leafing so much earlier than the 

 others. There is also an oak near Edinburgh which retains its 

 leaves to a very late period. These differences have been attributed 

 by some authors to the nature of the soil in which the trees grow ; 

 but Archbishop T\ nately grafted an early thorn on a late one, and 

 vice versa, and both grafts kept to their proper periods, which 

 differed by about a fortnight, as if they still grew on their own 

 stocks. 158 There is a Cornish variety of the elm which is almost 

 an evergreen, and is so tender that the shoots are often killed 

 by the frost; and the varieties of the Turkish oak (Q. cerris) may 

 be arranged as deciduous, sub-evergreen, and evergreen. 159 



Scotch Fir {Pinits sylvestris). — I allude to this tree as it bears on 

 the question of the greater variability of our hedgerow trees com- 

 pared with those under strictly natural conditions. A well-informed 

 writer 160 states that the Scotch fir presents few varieties in its 

 native Scotch forests; but that it ''varies much in figure and 

 " foliage, and in the size, shape, and colour of its cones, when several 

 " generations have been produced away from its native locality." 

 There is little doubt that the highland and lowland varieties differ 

 in the value of their timber, and that they can be propagated truly 



156 Godron, ' De l'Espece,' torn, ii. 15S Quoted from Royal Irish Aca- 

 p. 89. In Loudon's ; Gardener's Mag.,' demy in ' Gardener's Chron.,' 1841. p. 

 vol. xii., 1836, p. 371, a variegate! 767. 



bushy ash is described and figured, as 159 Loudon's 'Arboretum et Fruti- 



having simple leaves ; it originated in cetum :' for Elm. see vol. iii. p. 1376 ; 



Ireland. for Oak. p. 1846.' 



157 'Gardener'/ Chxon.,' 1863, p. 160 ' Gardener's Chronicle,' 1849, p t 

 575. 822. 



