Vl] DEVELOPMENT OF FORM 67 



an average length about equal to that of the lower ones — 

 which also slow down their growth with age — so that 

 what was a pointed conical crown becomes a blunt cylin- 

 droidal tree, a state of atfairs often realised in the Silver 

 Fir (Fig. 15). 



Now let us suppose that a tree which has reached the 

 condition just described begins to lose its low^ermost, older 

 branches altogether : that they die off in succession as 

 the tip did, aud are gradually removed by high winds as 

 the dead sticks become more and more brittle, or by the 

 various other agencies which lead to the self-pruning of 

 trees in Nature. The first consequence may be the setting 

 free of the lower part of the stem as a clean bole, the 

 upper part of which still carries the upper part of the 

 crown, the branches of which still retain their average 

 capacity for growth and elongate more or less equally. 

 This will result in the conversion of the previously cylin- 

 droid crown to a more or less ovoid, oblong or ellipsoidal 

 one, a condition often seen in Scots Pine, Austrian Pine 

 and others (Fig. 16). 



But we also suppose the pointed-conical form to be 

 preserved under similar conditions of denudation of the 

 bole, if that process occurs before the leader has stopped 

 growing, and if the relative growth of the branches is 

 preserved : indeed, if the lower main branches keep up 

 their growth vigorously, such figures as the broadly 

 pyramidal-conic form may result and be maintained for 

 many years. 



Even further changes of shape ensue in many of the 

 Pines, Cedars, &c. after the crown has passed through 

 a stage such as has just been described. While the 

 cleaning of the bole of lowermost branches proceeds, the 

 leader ceases to grow, but the lateral branches below it 

 continue to spread. The consequence is a more or less 



5—2 



