General Considerations 205 



ditions, but also local soil conditions will cause one tree 

 to bud out earlier and retain its foliage longer than another 

 tree of the same species. That the length of leaf period is a 

 habit capable of inheritance is proved by the fact that sev- 

 eral of the exotics which are frequently planted have invari- 

 ably a longer leaf period than native species of the same 

 genus; the European elms, linden, and maples are examples. 



Another very important point, also often overlooked, is 

 that the form of crown changes from the young to the old 

 tree: there is a beauty of youth and a beauty of maturity, 

 while adolescence is often marked, as in man, by awkward 

 and unsatisfactory looks. This is especially the case with 

 conifers; for the change from the shapely conical young form 

 to the broad stately umbrella-shape or the compactly globular 

 or ascending rhomboidal form of old age, interposes a less 

 pleasing, longer or shorter, intermediary stage. The descrip- 

 tion of the outline or form of a tree can therefore refer only 

 to one period of its life, usually the mature stage. 



In selecting rare species which nurserymen are apt to prop- 

 agate by grafting on other stocks, it should not be over- 

 looked that these stocks may produce undesirable results: 

 a different rate of growth may cause bulging at the juncture, 

 the lower trunk being either more rapid or less rapid than 

 the graft in gaining diameter, or the fohage may revert to 

 that of the mother stock, etc. Hence, in purchasing such 

 grafted trees we must assure ourselves that experience has 

 proved the stock upon which the graft is made as trust- 

 worthy. 



The same disappointment which we may experience in 

 the form development, by virtue of unsuitable soil conditions 

 may, of course, extend to the shading value and to the rate 

 of growth. The tree which in a rich soil developed a mag- 

 nificent canopy of fohage will be scantily furnished in a 



