360 HORTICULTURE, FORESTRY, FLORICULTURE 



suffering the disadvantages resulting from too open stand. The 

 solution of this problem requires the greatest skill and judgment, 

 and rules can hardly be formulated with precision, since for every 

 species or combination of species and conditions these rules must be 

 modified. In a well-established young crop the number of seedlings 

 per acre varies greatly, from 3,000 to 100,000, according to soil, 

 species, and the manner in which it originated, whether planted, 

 sown or seeded naturally. Left to themselves, the seedlings, as they 

 develop, begin to crowd each other. At first this crowding results 

 only in increasing the height growth and in preventing the spread 

 and full development of side branches; by and oy the lower branches 

 failing to receive sufficient lignt finally die and break off the shaft 

 "clears itself." Then a distinct development of definite crowns takes 

 place, and after some years a difference of height growth in different 

 individuals becomes marked. Not a few trees fail to reach the gen- 

 eral upper crown surface, and, being more or less overtopped, we can 

 readily classify them according to height and development of crown, 

 the superior or "dominating" ones growing more and more vigor- 

 ously, the inferior or "dominated" trees falling more and more be- 

 hind, and finally dying for lack of light, and thus a natural reduc- 

 tion in numbers, or thinning, takes place. This natural thinning 

 goes on with varying rates at different ages, continuing through the 

 entire life of the crop, so that, while only 4,000 trees per acre may be 

 required in the tenth year to make a dense crown cover or normally 

 close stand, untouched by man, in the fortieth year 1,200 would 

 suffice to make the same dense cover, in the eightieth year 350 would 

 be a full stand, and in the one hundredth not more than 250, ac- 

 cording to soil and species, more or less. As we can discern three 

 stages in the development of a single tree the juvenile, adolescent, 

 and mature so, in the development of a forest growth, we may dis- 

 tinguish three corresponding stages, namely, the "thicket" or brush- 

 wood, the "pole-wood" or sapling, and the "timber" stage. During 

 the thicket stage, in which the trees have a bushy appearance, allow- 

 ing hardly any distinction of stem and crown, the height growth is 

 most rapid. This period may last, according to conditions and spe- 

 cies, from 5 or 10 to 30 and even 40 years longer on poor soils and 

 with shade-enduring species, shorter with light-needing species on 

 good soils and, while it lasts, it is in the interest of the wood grower 

 to maintain the close stand, which produces the long shaft, clear of 

 branches, on which at a later period the wood that makes valuable, 

 clear timber, may accumulate. Form development is now most im- 

 portant. The lower branches are to die and break off before they be- 

 come too large. With light-needing species and with deciduous trees 

 generally this dying off is accomplished more easily than with coni- 

 fers. The spruces and even the white pine require very dense shad- 

 ing to "clear" the shaft. During this period it is only necessary to 

 weed out the undesirable kinds, such as trees infested by insect and 

 fungus, shrubs, sickly, stunted, or bushy trees which are apt to 

 overtop and prevent the development of their better neighbors. In 



