2 HABIT [CH. I 



crown, because several or even many spring direct from 

 the soil, and assume equal importance in the formation of 

 the leafy crown. 



Thus far matters are simple enough, but while a lofty 

 tree such as a well-grown Oak, Beech, or Elm, or an old 

 Scots Pine, exhibits an unmistakable trunk 20 to 60 or 

 more feet in height, plenty of examples may be found 

 where the branches of the crown arise so low down that 

 even the very thick bole is only a few feet, or even only 

 a foot or two high in the clear, and the form approaches 

 very nearly to that of the shrub. 



The position is complicated by the existence of very 

 many trees in which no definite crown is developed until 

 very late in life, as in numerous species of Pines and Firs 

 which put out branches at all heights from base to apex 

 and maintain them for a large number of years ; and even 

 tall Elms, 80 to 100 years old, may be thus clothed from 

 top to toe with foliage-bearing shoots, and the crown 

 can no longer be regarded as a head but must be looked 

 upon as distributed over the whole trunk, the superior 

 length and massiveness of which alone fit the accepted 

 definition of a tree. 



Further complication arises from the fact that natural 

 or artificial interference with the normal development of 

 the tree often imposes upon it an approach to the form 

 of a shrub. Examples in abundance are provided in 

 situations where extremes of climate, or the recurrent 

 breaking weight of snow and ice, the pressure of wind, &c.> 

 bring about repeated dwarfing or fracture of the main 

 stem, or of any strong branch which attempts to rise to 

 the proportions of such : for instance, the dwarf shrubby 

 Birches of sub-arctic or alpine regions, or the stunted Oaks, 

 Hawthorns, &c., near sea-coasts, and so forth. Illustrations 

 of the incidence of artificial conditions are afforded by the 



