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Some Fallacies of the Forest 



ARTICLE TWO 



Docs liii- ^in> iM-r go up or eMi ^-ii ilnwii iii ;i true? Does the 

 trunk I'outaiu more of it m summer tban in winter? Does it flow 

 upward in spring and down in the fall? Tbeso three questions are 

 really the same one asked in a slightly dift'erent way each time. Most 

 people will answer with a plain yes or no; and probably nine out of 

 ten will say yes. 



The majority rules in politics, and if it ruled in the same way in 

 science, the question would be speedily settled. There is a pretty 

 broad difference between ruling and proving. Matters are ruled by 

 the ballot in politics; but in science they are proved, and until there 

 ^ proof, nothing is settled. The vote of the whole world, or as much 

 • f it as cared to vote, was against Galileo, yet the question of the 

 movement of the earth was finally settled his way. Most people say 

 that a tree's sap goes up in the spring and comes down in the fall, 

 but is that really what happens? 



It ought not take long to make a rough test. Are green logs any 

 lighter if cut in dead of winter than in the height of summer? The 

 s.'alcs fail to show it. If sununer cut logs weigh 10,000 pounds to 

 the thousand feet, log scale, the same kind of logs cut in winter will 

 weigh about the same. If the sap goes down in the fall the winter 

 logs ought to bo lighter by several thousand pounds, since it is well 

 known that green wood is nearly half sap. 



The sap of a tree is not exactly the same thing to all people who 

 think of it; but the usual conception is that it is the liquid contained 

 in the trunk, leaves, and branches. That definition i.s accurate enough 

 for practical purposes. The water finds it way into the trunk through 

 the roots — with slight exceptions in some instances. The fine hairs 

 on the roots pull the water out of the soil and start it up the trunk 

 through minute vessels which constitute the structure of the wood. 

 It makes its way to the remotest branches. 



It is an old and homely, though unscientific, saying that ' ' what- 

 ever goes up has to come down." The water that goes up a tree 

 trunk comes pretty nearly being an exception. Of course, it comes 

 back to earth sometime, since it does not stay up the tree forever. 

 and does not go off into planetary space; but it does not come back 

 by the paths it followed in ascending. 



The sap that goes up a tree is soil water. It contains certain 

 earthy ingredients in small amounts. Much of it enters the tree 's 

 leaves in summer, where a sort of chemical laboratory is at work, and 

 the water and whatever else it contains are used in manufacturing 

 food to build up the tree, add on new wood, and supply a reserve 

 for the time when the leaves will not be in the manufacturing busi- 

 ness, that is, the next winter. 



In making this food, the leaves get rid of a lot of the water that 

 lame up from the roots. It passes out through minute openings in 

 the leaves and is evaporated, going into the air to be blown away. 

 Most of the wafer that goes in through the roots, passes out through 

 the leaves, and that is the last of it, as far as that particular tree is 

 foncorned. It "goes up" but it never "comes down." 



Though most of the water escapes through the leaves and disap- 

 pears, the residue makes a longer or shorter downward journey in the 

 summer. The plant food manufactured in the leaves must be carried 

 to the places where it is needed and the remnant of the water is 

 utilized for this purpose. The starches, sugars, resins, etc., produced 

 in the leaves are carried downward through the trunk to be de- 

 yjosited just beneath the bark where they form the new lay^r of wood. 

 This new wood forms all the way from the roots to the twigs, and 

 the water or sap distributes the substances that produce it. A very 

 small part actually may return to the ground whence it came, and 

 to that extent the sap may go down, but even that small part does 

 not go down in the autumn, but in the summer, and most of it pretty 

 early. 



The water, laden with food materials, that starts from the leaves 

 downward, nearly all disappears in the course of its journey. When 

 a particle of this water (which during its downward journey is prop- 



erly calleil sap) gives up its load of starches and the like, it is no 

 longer of any use to the tree, and is gotten rid of by being forced 

 out through small holes in the bark, called leuticels. Quito a large 

 amount of water thus passes away. The lenticels of some trees are 

 conspicuous objects on the bark. Young birches and cherries show 

 their location by horizontal markings from half an inch to a couple 

 inches in length. 



Tho circulation of sap in the trunk and branches of a tree is 

 chiefly through the sapwood and the bark. The interior or heart- 

 wood is practically dead, though it is always filled with water, more 

 or less. The amount of water which rises through a tree's trunk 

 seems to bo largely dependent upon the quantity the leaves can use 

 in their processes. The leaves generally have all they need, but 

 such is not always the case. In long periods of drought the roots 

 may fail to send up enough water to supply the leaves. In that case, 

 the leaves may wither or fall prematurely, and the tree's growth will 

 be retarded. At any rate, when the leaves fall, whether prematurely 

 or not, the water in the trunk practically ceases to circulate, although 

 some change from place to place occurs." It is certain that no gen- 

 eral retreat down the trunk to the roots takes place, such as is sup- 

 posed by those who speak of ' ' sap going down. ' ' 



Gravity appears to produce little effect on the sap. At least, it 

 is not able to pull it down after the action of the leaves ceases to 

 pump it up. It is not much out of the way to state that when the 

 activity of the leaves ceases in autumn, whatever water is in the tree 

 at that time lies inert until the following spring when the opening 

 leaves again begin to lift the water by means of their billions of 

 little pumps, and the whole process begins anew. 



Though the wood of a living tree contains a large amount of water 

 at all times, it does not usually flow out when a cut is made into the 

 wood; though certain trees, as maple and birch, lose a considerable 

 quantity of water if the trunk is cut in spring. That is popularly 

 supposed to be due to the "rising" of the sap. It does not appear 

 to be wholly certain just why the flow comes at that time, but it un- 

 questionably begins before the frozen soil about the roots has thawed 

 sufliciently to admit ground water to start up the trunk. The matter 

 can be tested by building a fire against the trunk of a maple tree in 

 dead of winter. As soon as the wood near the fire is thawed, sap 

 will flow from a wound. Pioneer settlers sometimes made small 

 quantities of maple sugar in mid-winter by building fire to warm the 

 wood, though the roots were frozen solid. Evidently the sap was 

 in the wood, and did not get there by rising from the roots after the 

 fires were built. 



When weather is warm, leaves of nearly full size, and everything 

 favorable, water ascends the trunk of a tree quite rapidly. The rate 

 varies greatly, and many measurements have been made. Proof of 

 the quickness with which the water goes from the base to the high- 

 est branches can be had in early summer by girdling a vigorous 

 youug red oak, cutting entirely through the sapwood all round. In 

 a very short time the leaves begin to wither, indicating that the 

 water supply is failing. When hardwood trees are being cut while in 

 full leaf tho rapidity with which the failing sap supply is shown by 

 withering leaves is an interesting study. Some kinds show the effect 

 within a few hours, others do not wither for several days. The soft 

 woods, such as pine and hemlock, seem to feel the effect of a cut-off 

 in the supply only after many days. 



When a tree in full leaf is cut down, the leaves go on pumping 

 water from the trunk and discharging it into the air, until the supply 

 in the trunk is reduced so low that the leaves can draw in no more 

 of it. Then they wither. Tho wood of a fallen tree can be partly 

 seasoned by leaving the trunk untrimmed for a few days thereby 

 giving the leaves time to draw tho water out of the wood. The 

 quantity thus extracted is measurable, but it is only a small per cent 

 of the total water in the trunk. As soon as the quantity is slightly 

 reduced, the leaves are no lon^jpr able to obtain any more. 



