362 



TEEES. 



Chap. X. 



thus see the same result following from the effects of climate and from 

 an innate spontaneous tendency. 150 



In foliage we have variegated leaves which are often inherited; dark 

 purple or red leaves, as in the hazel, barberry, and beech, the colour in 

 these two latter trees being sometimes strongly and sometimes weakly 

 inherited; 151 deeply-cut leaves; and leaves covered with prickles, as in 

 the variety of the holly well called ferox, which is said to reproduce itself 

 by seed. 152 In fact, nearly all the peculiar varieties evince a tendency, more 

 or less strongly marked, to reproduce themselves by seed. 153 This is to a 

 certain extent the case, according to Bosc, 154 with three varieties of the 

 «lm, namely, the broad-leafed, lime-leafed, and twisted elm, in which 

 latter the fibres of the wood are twisted. Even with the heterophyllous 

 hornbeam (Carpinus betulus), which bears on each twig leaves of two shapes, 

 " several plants raised from seed all retained the same peculiarity." 155 I 

 will add only one other remarkable case of variation in foliage, namely, the 

 occurrence of two sub-varieties of the ash with simple instead of pinnated 

 leaves, and which generally transmit their character by seed. 150 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 

 pendula or filiformis 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. orientalis; and Dr. Hooker has adduced 

 excellent evidence that at Turin seeds of T. pendula have reproduced the 

 parent-form, T. orientalis} 57 



Every one must have noticed how certain individual trees regularly 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 



m 



i)?< 



150 Godron (' De l'Espece,' torn. ii. 

 p. 91) describes four varieties of Bo- 

 binia remarkable from their manner of 

 growth. 



151 ' Journal of a Horticultural Tour, 

 by Caledonian Hort. Soc.,' 1823, p. 107. 

 Alph. De Candolle, ' Geograph. Bot.,' 

 p. 1083. Verlot, ' Sur la Production des 

 Varietes/ 1865, p. 55, for the Barberry. 



152 Loudon's 'Arboretum et Fruti- 

 cetum,' vol. ii. p. 508. 



153 Verlot, <DesVarietes,'1865,p.92. 



154 Loudon's ' Arboretum et Fruti- 

 cetum,' vol. iii. p. 1376. 



155 ' Gardener's Chronicle,' 1841, p. 

 687. 



156 Godron, ' De l'Espece,' torn. ii. p. 

 89. In Loudon's ' Gardener's Mag.,' 

 vol. xii. 1836, p. 371, a variegated bushy 

 ash is described and figured, as having 

 simple leaves ; it originated in Ireland. 



15 ' ' Gardener's Chron.,' 1861, p. 575. 



