6 HABIT [CH. 



bush is a small tufted shrub are not totally devoid of 

 practical significance : we may still insist on the fact that 

 many plants normally direct a maximum of growth -energy 

 into one principal stem from the first and maintain this 

 for many years, the result being a tree with a thick, 

 woody trunk or bole : whether this eventually bears all 

 its branches above only, as in old Oaks and Pines, or bears 

 them along its course as in the Common Elm and Firs, 

 whether the trunk is traceable to the top of the whole 

 tree as in most Conifers, or soon breaks up into dividing 

 or forking branches as in Beeches, Maples, &c., whether 

 the whole is large and tall as in normal Larches, Ash, &c., 

 or small and low as in Hawthorn, Box, &c., are incidents 

 partly dependent on the specific nature of the tree, and 

 beyond our explanation at present, but partly due to the 

 action of the environment and often definitely referable to 

 such. 



And similarly with shrubs and bushes. There are 

 some, such as certain Willows, Brambles, &c., which prob- 

 ably never assume the tree-form, in the sense of elevating 

 a single trunk bearing a crown ; others, as many climbing 

 plants e.g. Clematis, Ivy, &c. which have special forms 

 quite distinct in their kind ; others again which though 

 usually shrubs can be readily forced into the tree-form 

 by pruning and cultivation e.g. Primus spinosa, Bar- 

 berry, &c.; and yet others which will normally develope 

 into small or even fairly large trees, but are usually met 

 with as shrubs e.g. Hawthorn, Holly, Yew, Hazel, &c. 



Possibly any shrub could be compelled to assume the 

 tree-form, or an approach to it, by suitable cultural treat- 

 ment, and it has already been shown that many trees 

 are habitually forced into the shrubby habit by pruning, 

 coppicing, &c. Of course we are not here concerned with 

 the extreme cases of trees which become bushy at the 



