1868. 



NEW ENGLAND FARRIER. 



377 



CIKCUIiATION OF SAP. 



The late article of our correspondent, "C. 

 N. A.," on the source of the saccharine mat- 

 ter in the sap of maple .trees, and on the 

 causes and conditions of its flow, was well 

 calculated to excite thought and inquiry. 



In reading the new edition of Waring's 



"Elements of Agriculture," noticed last week, 



we found the following illustration of the 



manner in which food is taken up by the 



"spongioles" or mouths of the roots of plants, 



— an illustration, by the way, which we had 



some trouble in referring to after we had shut 



up the book, from the want of an alphabetical 



index to subjects ; an omission that we can 



hardly excuse in any book-maker. We found 



it at last, however, on pages 36 and 37, as 



follows : 



Take a tumbler, filled entirely full with water; 

 tie over it a bladder, and on tlie bladder sprinkle a 

 little salt. The bladder becomes moist throughout 

 its entire thickness, and transmits enough mois- 

 ture to the salt to dissolve it gradually, and as fast 

 as it is dissolved, it passes through the bladder 

 into the water inside of the tumbler. In a long 

 enough time the water can be made, in this way, 

 to dissolve as much salt as though it had been 

 stirred into it without the intervention of the blad- 

 der. If we keep the salt soaking wet, as it lies on 

 the outside of the bladder, it will pass through 

 much more rapidly, but if we do not wet it by a 

 direct application of water, enough water will 

 reach it through the membrane to allow it to pass 

 into the tumbler, as above described. The roots 

 of plants contain sap, which is separated from the 

 plant-food in the soil, by a thin film of matter, 

 which constitutes its cell-walls. So long as the 

 water of the sap has the capacity to dissolve more 

 mineral matter than it already contains, it will 

 take it through the cell-walls, as the salt is taken 

 through the bladder. If the plant-food outside of 

 the roots is in a moist condition, it will be taken 

 up more rapidly than if too dry. The moistiu'e of 

 the soil itself, containing mineral matter in solu- 

 tion, passes through the cell-walls to supply the 

 place of that which has been evaporated at the 

 leaves, the matters in solution passing through 

 with the water itself. ^ 



We are also glad to see that the editor of 

 the Boston Cultivator, who is versed in the 

 science of botany, has let in a few rays of 

 light on the "unusually visible darkness" in 

 which our correspondent thinks the remarks 

 of the editor of the Maine Farmer left the 

 subject. 



Experiments made by distinguished vegeta- 

 ble physiologists are cited, in which the stem 

 of trees were tapped, at different heights from 

 the ground, for the purpose of ascertaining 

 the points where the sap made its first appear- 

 ance. In all the cases mentioned the exdua- 

 tion of sap in the spring occurred earlier in 

 the lower than in the upper part of the trunk, 



tending to show that the /t«(i portion, at least, 

 of the sap comes-fromthe "cold, dark ground." 



As to the amount of sap in vines and trees, 

 Keith's Botanical Lexicon, (London,) is given 

 as authority for the assertion that "a small 

 branch of a vine has been known to yield from 

 twelve to sixteen ounces in the space of 

 twenty-four hours ; a maple of moderate size 

 yields about 200 pints in a season; and a 

 birch tree has been known to yield a quantity 

 equal to its own weight. 



As to its chemical composition, reference is 

 had to "Ann. de Chim." for the remarks that, 

 if exposed to the action of fire, sap emits 

 bubbles of carbonic acid gas, exhales a strong 

 odor of vinegar, and yields by distillation car- 

 bonate of ammonia. It combines in all pro- 

 portions with water, which dilutes and dis- 

 solves it when thick and viscid. Alkalies com- 

 bine with it readily, and saturate its excess of 

 acid. In the sap of Fagus syhatica, Vau- 

 quelin found the following ingredients : water, 

 acetate of lime with excess of acid, acetate of 

 potass, galls, acid, tannin, mucous and extrac- 

 tive matter, and acetate of alumina. 



But the most satisfactory statement is found 

 in the following quotation from "E. Darwin, 

 M. D., F. R. S.," which we copy entire. 



"The ascending sap-juice during the spring sea- 

 son is in some trees so sweet, that it is used in 

 making wine, as that of the birch tree in this 

 country; and sugar is procured in such quantity 

 from a maple in Pennsylvania, that from each tree 

 five or six pounds of good sugar have been made 

 annually without destroying it. (Rush, on Sugar 

 Maple. Philips, London.) This sugar is deposited, 

 I believe, in the sap-wood of the trunk and roots 

 of trees, as in the manna-ash, and is dissolved in 

 the spring by the moisture, which is drunk up. by 

 the absorbents from the earth and atmosphere, and 

 .forcibly carried on to expand the buds. Its exis- 

 tence in the sap-wood as well as in the root is 

 shown from the pullulation of oak trees, which 

 have been stripprd of their bark, and also from the 

 expansion of the eyes of a vine shoot, when it is 

 cut from the tree, iind planted in the earth. 



This suggests to us the reason why the wood of 

 trees is so much i-ooner subject to decay, when 

 they are felled in the vernal months ; because the 

 sugar, which the sap-wood then contains, soon runs 

 into fermentation, and produces what is called the 

 dry rot ; whence the custom has prevailed of de- 

 barking oaks in the spring, and felling them in the 

 autumn ; and it is probaJile that the wood of all 

 other trees would last much longer, if it was thus 

 managed, as the growth of the new leaves would 

 exhaust the sugar of the sap wood. 



Sweet juices for a similar purpose of expanding 

 the buds of herbaceous plants are deposited dur- 

 ing the autumn in their roots, as in turnip, beet, 

 tragapogon ; or in the knots or joints of the stem, 

 as in grasses, and the sugar-cane ; which like the 

 farina and oil in seeds, aud the dulcet mucilage of 

 fruits, and the honey of€lowers, were designed for 

 the food of the young progeny of plants, but be- 

 come the sustenance of mankind ! 



