. The principles of agriculture; a text-book for schools and rural societies . 126 THE PRINCIPLES OF AGRICULTURE flower. Fit tightly over this stub a few inches of rubber tubing,partially filling the tubing with water, and into the free end fitclosely a small glass tube several feet long, supporting the tubeby a stake. In a few hours water will begin to rise in the glasstube. This pressure in the common nettle may sustain a columnof water over ten feet in height, and in the grape-vine a columnmore than thirty feet in height. It is inapplicable for plants thatforce up only a small volume of wat
. The principles of agriculture; a text-book for schools and rural societies . 126 THE PRINCIPLES OF AGRICULTURE flower. Fit tightly over this stub a few inches of rubber tubing,partially filling the tubing with water, and into the free end fitclosely a small glass tube several feet long, supporting the tubeby a stake. In a few hours water will begin to rise in the glasstube. This pressure in the common nettle may sustain a columnof water over ten feet in height, and in the grape-vine a columnmore than thirty feet in height. It is inapplicable for plants thatforce up only a small volume of water under high pressure. 189&. The sap ascends through the young woody parts,—the sap-wood in our common trees, and not between the bark andwood, as commonly supposed. To note the special channels. Cross-section of a leaf. FotiT stomata. through which sap ascends, secure a few joints of green com,a blade of celery, a leaf of canna, and some woody branch, andput the stem ends into a tumbler with a solution of some reddye or stain, preferably eosin or fuchsin. Oft^n in the courseof a few hours there is external evidence that the colored liquidascends through definite channels, at least with the succulentherbs. Now cut off the st«ms and note the colored regions,—in the com those thread-like groups of fibers so noticeable whenan old cornstalk is broken ; in the celery, likewise, through thosestringy fibers known to all who have eaten tough celery ; andin woody plants, through the layers of wood nearest the bark. 190o. For fuller discussions of the subjects outlined in 190ind 191, consult Sorauer, ^Physiology of Plants for the Use ofGardeners, pp. 30-44, 48-51. HOW THE PLANT LIVES 127 194a. Air in which seeds have been germinating has suffereda change; this can be shown in the fol
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