r6 



HARDWOOD RECORD 



Tree Growth and the Pht;stcs of Wood. 



Fonnation and Function of the Leaf. 



John Euskiu, in Modern Painters, says of 

 the leaf-worker: "It leads a life of en- 

 durance, effort, and various success, issuing in 

 various beauty; and it connects itself with the 

 whole previous edifice by one sustaining 

 thread, continuing its appointed piece of work 

 all the way from top to root. ' ' 



Not until we interest ourselves thoroughly 

 in tree life do we begin to realize how strenu- 

 ous a worker and builder the leaf is, and how 

 important a part it plays, not only in the life 

 of a plant itself, but in our own lives, which 

 are inseparably connected with the trees and 

 greatly influenced by them. Accustomed as 

 we are to their presence, we are prone 

 to underestimate and even ignore their 

 value to us. The average child is of 

 an investigating turn of mind, and as 

 time goes on, becomes familiar with 

 most of the commoner objects about 

 him, yet how many play for years un- 

 der the shade of familiar trees, with- 

 out being able to tell an ash leaf fnuii 

 an elm, or a maple leaf from an oak! 



To understand the growth and im 

 portance of tree life, it is not enough 

 to be able to distinguish one tree from 

 the other; it is necessary to beeomi^ 

 familiar with the objects of their 

 existence, and the manner in which 

 those objects are attained. These facts 

 are revealed in no small degree by the 

 leaves. 



No two leaves are exactly alike, 

 neither are any two trees. The great 

 diversity of form in leaves is likewise 

 found in the trees themselves. In a 

 measure, a leaf may be an index to 

 the life of its parent. The pine needle 

 is slim, sharp, wiry and repellant, and 

 these very qualities enable the conifer 

 to lead a rugged, stormy but success- 

 ful existence upon some barren ridge. 

 The shiny, gossamer-like leaf of the 

 beech is characteristic of its careless, 

 uneventful life, which would be quickly 

 snuffed out were it subjected to the 

 fierce gales which the pine triumph- 

 antly weathers. 



Trees grow in two ways — they 

 thicken and lengthen. The former method 

 of growth' has been discussed in a previous 

 paper. The latter takes place by a sort of 

 ' ' telescopic extension ' ' at the buds or ex- 

 tremities. These in turn thicken and become 

 branches. Thus it is that a naU driven into 

 a tree-trunk at a given distance from the 

 ground is never any further from it. 



The perfect symmetry with which leaves 

 are placed upon a stem is maintained in 

 much the same way, even though the plant 

 becomes a great tree. The branches partake 

 of this symmetry to a greater or less degree, 

 inasmuch as they follow in the wake of the 

 leaves which preceded them. In the spring in 

 the axils of the leaves buds put in their ap- 



pearance. These tiny peepers are the sources 

 of later branches. In their growth they fol- 

 low the same process of development as did 

 the original little stem which burst from the 

 embryo between the cotyledons, the only dif- 

 ference being that the new leaves and 

 branches derive their nourishment from the 

 parent stem, while the tiny germ contained 

 within itself the life principle, and possessed 

 the power to extend itself upward, and down- 

 ward into the ground as well. They grow 

 with the same symmetry and by the system 

 of progression, one joint upon the other, each 

 lengthening and in its turn producing leaves 

 at its end. Then other buds develop in their 



FOLIAGE AXD FRUIT OF WHITE PINE. 



axils and gradually become prolific branches; 

 again and again is this wonderful process re- 

 peated until the entire tree is formed and 

 matured. 



Occasionally the axillary buds commence 

 their activity soon after first making their 

 appearance in the angles of the leaves, but 

 more often they remain dormant until the 

 following spring, when suddenly, within tlie 

 space of a few days or a week, a touch of 

 green appears about the edges of the pro- 

 tecting scales, they loosen and drop away, to 

 liberate the imprisoned shoot, which quickly 

 expands and extends to the sun its wrinkled 

 leaves. The tender bud is a complete shoot 

 in miniature — its little leaves and even the 



rudimentary blossoms already formed, and 

 most wonderfully and carefully protected by 

 Nature from cold and dampness. 



These sheaths or chambers are in many and 

 varied forms. Those of the horse-chestnut 

 are composed of many scales, so overlapped 

 about the delicate parts within as to insure 

 their preservation. The buttonwood has what 

 appears to be a peculiar extension or enlarge- 

 ment of the base of the .eaf-stalk, but when 

 the stalk is detached from its branch it is 

 found to be hollow and to fit down tightly 

 over the projecting leaf-bml. In northern 

 climates the leaf-scales which enclose the bud 

 are often lined with a downy substance, and 

 are rendered impervious to dampness 

 by a sort of glazing without. ' ' To 

 open one of these strong buds seems 

 almost like prying into futurity." All 

 that a tree will ever possess of beMuty 

 or vigor originates in the tiny buds, 

 enclosed all winter in their protecting 

 scales, but ready, as spring advances, 

 to respond to the slightest touch of 

 sun and warm south wind. 



Tlie stipules, or tlie pair of tiny 

 appendages at the base of the .young 

 shoot, are an added protection to it. 

 Most of them remain with the leaf 

 until it matures, and then fall away, 

 but others, notably the large, triangu- 

 lar ones of the black willow, are per- 

 sistent. The stipules are varied in 

 form ; sometimes they are in the form 

 of tendrils; again they are scales or 

 sjiines; those of the beech are long 

 and strap-like. 



After they are once expanded and 

 strengthened by the light of day, the 

 leaves take up vigorously the work for 

 which they are created. While these 

 visible changes are taking place above 

 ground the roots, hidden away in the 

 earth, are also at work uranching and 

 multiplying in order to hold the tree 

 firm as it increases in size. Often 

 the simple root which was first sent 

 down by the embryo remains the main 

 one, from which branches sjiring out- 

 ward, but usually it divides, and the 

 branches thus formed send out others. 

 The young roots absorb large quantities of 

 nourishment from the soil. To facilitate 

 this process they are frequently covered 

 thickly with root hairs, which easily imbibe 

 the moisture into their canals. 



It is from these rich young roots that the 

 sap is drawn upward to feed the leaves. This 

 ascension takes place principally through the 

 wood cells, although, contrary to the common 

 theory, these chambers are not connected 

 with each other in any way. The jirocess of 

 sap progression is by transfusion — it passing 

 through thin places in the walls of these cells. 

 Although at first thought, the rise of the sap B 

 into the topmost branches and leaves of a • 

 tree seems contrary to Nature's laws, there 



