Chap. 5.]
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and pear trees. By what wonderful process is sap distilled into liquidhoney in tlie maple, and mto wine in the grape 'ä How is it elaboratedinto fruits of every davor, and exhaled in perfumes from sweet scentedherbs, and in what manner does it contribute to produce every imaginablecolor and tint in flowers 1
By what means does sap form a natural vase in the pitcher plant, andthen enter it as lirnpid water, along with rain and dew % This singulärproduction of the vegetable kingdom collects water from the earth andatmosphere in vessels of the same consistence and color as the leaves.Each pitcher is strengthened by a hoop, and furnished with a cover or lidthat turns on.a fibrous hinge. When dew or rain falls, this cover opens ;and as soon as the weather clears, it closes and prevents the water thatentered from being wasted by evaporation. There are other plants whichstöre up water much in the same way. Such were the reeds that relievedAlvarado (one of the conquerors of Peru ) and his companions from perish-ing of thirst. Garcilasso, in his Commentaries observes, “ The Infor-mation they had of the water was from the people of the country, whoguided them to the canes, some of which contained six gallons, and somemore.”
We know that the juices of plants cannot be raised without force, andthat this force must be increased with the elevation to which the liquid isto be lifted. Animais exert a muscular power in working the pumpsformed in their bodies, and these machines they put in motion at will.This is not the case with vegetables : yet sap, the pabulum of their life,is elevated to the tops of the highest trees, and apparently with the samefacility as it is diffused through microscopic plants. That the force bywhich this is done is not latent or negative in its nature, is clear, since itmay easily be rendered manifest. Cut a branch from a vine in the springwhen the sap is rising, and Stretch a piece of india rubber over the endof the part that remains, secure it by thread wound round the stump, soas to exclude the air and prevent the wound from healing. In a littlewhile the caoutchouc will be swelled or bulged out by the exudingfluid, and it will continue to swell, however thick it may be, tili it burst.A few years ago we treated in this way some branches of an Isabellagrape vine, and afterwards applied to one of them a close vessel contain-ing mercury, in which the lower end of a long glass tube was immersedwith a view to measure the force excited. In four days the mercuryrose 36 inches in the tube, being pushed up by the sap which took itsplace in the vessel; and but for an accident, by which the apparatus wasbroken, it would probably have ascended still higher.
But this force, great as it was, is small when compared with that whichsends the, fluid through trees that grow on the Australian continent andislands. Some of these resemble single tubes, and are filled with a semi-fluid or soft pith. Tasman, the discoverer of Van Dieman’s Land, foundtrees there whose lowest branches were between 60 and 70 feet above theground. The Freiich expedition sent in search of the lamented Perouse,found on Cocos island a tree nearly 100 feet high, and only three inchesin diameter. It was of so hai-d a texture, that it resisted at first theheaviest blows of an axe; and when 'the pith was taken out, the thick*ness of the wood did not exceed jq of an inch—forming a perfect tube.But this tree was only half the height of some others in the same regions ;for several were seen whose diameters were only seven or eight inches,and whose tops towered upwards of 200 feet above the earth ! The forcethat drives sap to such elevations is wonderful indeed ; and could it beapplied as a mechanical agent, it would be resistless as steam. It might