654 



THE GARDEN AND FIELD. 



July, 1913 



XKe Life of a Tree 



From Bulletin 175, U.S.A. Dept. of Agriculture. 

 (Continued from April Issue.) 



— Annual Rings. — 

 It is correct to speak of these 

 rings of growth as " annual 

 rings," for as long as the tree is 

 growing healthily a ring is formed 

 each year. It is true that two 

 false rings may appear in one year, 

 but they are generally so much 

 thinner than the rings on each side 

 that it is not hard to detect them. 

 Very often thev do not extend en- 

 tirely around the tree, as a true 

 ring always does if the tree is 

 sound. Whenever the growth of 

 the tree is interrupted and begins 

 again during the same season, such 

 a false ring is formed. This hap- 

 pens when the foliage is destroyed 

 by caterpillars and grows again in 

 the same season, or when a very 

 severe drought in earl)^ summ.er 

 stops growth for a time, after late 

 frosts, and in similar cases. 



— Heartwood and Sap. — 

 An annual layer once formed does 

 not change in size or place during 

 the healthy life of the tree, except 

 that it is covered in time by other, 

 voungcr layers. A nail driven in- 

 to a tree 6 feet from the ground 

 will still be at the same height 

 after it is buried under 20 or 50 

 or 100 layers of annual growth. 

 But in most trees, like the oaks 

 and pines, the wood becomes 

 darker in color and harder after it 

 has been in the tree for some years. 

 The openings of its cells become 

 chocked so that the sap can no 

 longer run through them. From 

 living sapwood, in which growth is 

 going on, it becomes heartwood, 

 which is dead, because i% has no- 

 thing to do with growth. It is 

 sim])ly a strong framework which 

 helps to su])i)ort the living parts 

 of the tree. This is why hollow 

 trees mav flourish and bear fruit. 

 When the tree is cut down, the 

 sajjwood rots more easily than 

 the heartwood, because it takes up 

 water readily and contains plant 

 food, which decays very fast. Not 

 all trees have heartwood, and in 

 many the difference in color be- 

 tween it and the sapwood is very 

 slight. Since water froip the 

 roots rises only in the sapwood, it 

 is easy to kill trees with heart- 

 wood by girrlling them, provided 

 all the sapwood is cut through. 

 But in those whoch have no heart- 

 wof)d the tubes of the older layers 

 of wood can still convey water to 

 the crown, and when c'l trees are 

 girdled it is often several years 

 before they die. 



A great many theories have been 

 proposed to accovmt for the rise 

 of water into the tops of tall trees, 

 some of which, as in the big trees 

 of California, ' may be over 300 feet 

 from the ground. But' none of 

 these theories is quite satisfactory, 

 and it .must be admitted that we 

 do not yet know how the trees 

 supply their lofty crowns with the 

 water which keeps them alive. 



— Trees in the Forest. — 



The nature of a tree, as shown 

 by its behavior in the 'forest, is 

 called its silvicultural character. It 

 is made up of all those qualities 

 upon which the species as a whole, 

 and every individual tree, depend 

 in their struggle for existence. The 

 regions in which a tree will live, 

 and the places where it will flour- 

 ish best ; the trees it will grow 

 with, and and those which it kills 

 or is killed by ; its abundance or 

 scarcity ; its size and rate^ of 

 growth — all these things are decid- 

 ed by the inborn qualities or silvi- 

 cultural character, of each particu- 

 lar kind of tree. 



— The Various Requirements of 

 Trees. — 



Different species of trees, like 

 different races of men, have spe- 

 cial requirements for the things 

 upon which their life depends. 

 Some races, like the Rskimos, live 

 only in cold regions. Others, like 

 the South Sea Islanders, must have 

 a very warm climate to be com- 

 fortable, and are short-lived, in 

 any other. So it is with trees, 

 except that their different needs 

 are even more varied and distinct. 

 Som.e of them, like the willows, 

 birches, and spruces , of northern 

 Canada, stand on the boundary of 

 tree growth. Many other species 

 grow onlv in tropical lands, 

 and can not resist even the lightest 

 frost. It is always the highest 

 and lowest temperature, rather 

 than the average, which decides 

 where a tree will or will not grow. 

 Thiis the average temperature of 

 an island where it never freezes 

 may be only 60 degrees, while an- 

 other place, with an averat^e of 70 

 degrees, may have occasional 

 frosts. Trees which could not live 

 at all in the latter on account of 

 the frost might flourish in the 

 lower average warmth of the for- 

 mer. 



In this wav the influence of 

 heat and cold on trees has a great 



deal to do with their distribution 

 over the surface of the whole 

 earth. Their distribution within 

 shorter distances also often de- 

 pends largely upon it. Even the 

 opposite sides of the same hill 

 may be covered with two different 

 species because one of them resists 

 the late and early frosts and the 

 fierce mid-day heat of summer, 

 \vhile the other requires the cool- 

 ness and moisture of the northern 

 slope. On the eastern slopes, 

 where the sun strikes early in the 

 day, frosts in the spring and fall 

 are far more apt to kill the voimg 

 trees or the blossoms and twigs of 

 older ones than on those which 

 face to the west and north, where 

 growth begins later in the spring, 

 and where rapid thawing, which 

 does more harm than the freezing 

 itself, is less likely to take place. 



— Requirements of Trees for Heat 

 and Moisture. — 



Heat and moisture act together 

 upon trees in such a way that it 

 is sometimes hard to distingTiish 

 their effects. A dry country or a 

 dry slope is apt to be hot as well, 

 while a cool northern slope is al- 

 most always moister than one 

 turned toward the south. Still the 

 results of the demand of trees for 

 water can usually be distinguish- 

 ed from the results of their need of 

 warmth, and it is found that mois- 

 ture has almost as great an influ- 

 ence on the distribution of trees 

 over the earth as heat itself. In- 

 deed, within any given region it is 

 apt to be much more conspicuous, 

 and the smaller the region the more 

 noticeable often is its effect, be- 

 cause the contrast is more strik- 

 ing. Thus it is frequently easy to 

 see the difference between the trees 

 in a swamp and those on a dry 

 hillside nearby, when it would be 

 far less easy to distinguish the 

 general character of the forest 

 which includes both swamp and 

 hill.side from that of another 



K. BECHTEL, 



SADDI.ER, TRUSS & BANDAGE 

 MAKER. 



59 O'Connell Street, 

 NORTH ADELAIDE... . 



Patent Attachable! and Detachable 

 Buggy, Spring Cart, Yankee, and Cab 

 Saddles. 



Truasea, Bandas^es, iKneccaps, Ijeather 

 .Jackets, Shoulder Straps, etc., Made 

 to Order, and sent to all parts of the 

 Commonwealth. Fit Guaranteed.. 



LADY IN ATTENDANCE 



