The New York Botanical Garden

To replace defective copy of the same date. Vol. Ill JULY, 1902 No. 31 JOURNAL The New York Botanical Garden EDITOR DANIEL TREMBLY MACDOUGAL Director of the Laboratories CONTENTS PACK The Temperature of the Soil 125 Effect of Lightning on Trees "31 June Meeting of the Horticultural Society of New York 135 Report of Mr. F. S. Earle on a Trip to Texas and New Mexico 137 The Plant Picture Collection 139 Notes, News and Comment 140 PUBLISHED FOR THE GARDEN AT 41 NOBTH QUBBN STRBBT, LANCASTER, PA BY THB NEW ERA PRINTING COMPANY OFFICERS, 1902. PRESIDENT—D. O. MILLS, VICE-PRESIDENT—ANDREW CARNEGIE, TREASURER—CHARLES F. COX, SECRETARY—N. L. BRITTON. BOARD OF MANAGERS. 1. EI.ECTED MANAGERS. ANDREW CARNEGIE, J. PIERPONT MORGAN, CHARLES F. COX, GEORGE W. PERKINS, W. BAYARD CUTTING, JAMES A. SCRYMSER, WILLIAM E. DODGE, SAMUEL SLOAN, JOHN I. KANE, W. GILMAN THOMPSON, D. O. MILLS, SAMUEL THORNE. 2. EX-OFFICIO MANAGERS. THE PRESIDENT OF THE DEPARTMENT OF PUBLIC PARKS, HON. WILLIAM R. WILLCOX. THE MAYOR OF THE CITY OF NEW YORK, HON. SETH LOW. 3. SCIENTIFIC DIRECTORS. PROF. L. M. UNDERWOOD, Chairman. HON. ADDISON BROWN, PROF. C. F. CHANDLER, HON. CHAS. C BURLINGHAM, PROF. J. F. KEMP, DR. NICHOLAS MURRAY BUTLER, PROF. H. H. RUSBY, GARDEN STAFF. DR. N. L. BRITTON, Director-in-Chief. DK. D. T. MACDOUGAL, First Assistant. DR. JOHN K. SMALL, Curator of the Museums. DR. P. A. RYDBERG, Assistant Curator. DR. ARTHUR HOLLICK, Assistant Curator. DR. MARSHALL A. HOWE, Assistant Curator. F. S. EARLE, Assistant Curator. GEORGE V. NASH, Head Gardener. ANNA MURRAY VAIL, Librarian. DR. H. H. RUSBY, Curator of the Economic Collections. DR. WM. J. GIES, Consulting Chemist. COL. F. A. SCHILLING, Superintendent. JOHN R. BRINLEY, Landscape Engineer. WALTER S. GROESBECK, Clerk and Accountant. CORNELIUS VAN BRUNT, Honorary Floral Photographer. JOURNAL OF The New York Botanical Garden VOL. III. July, 1902. No. 31. THE TEMPERATURE OF THE SOIL. A committee on the "Relation of Plants to Climate" was appointed at the New York meeting of the American Associa tion for the Advancement of Science, in June, 1900, and this committee immediately undertook the consideration of current methods of measuring temperatures with regard to their influence upon vegetation. The actual investigations planned by the com mittee were carried out by the author, and a paper was presented at the Denver meeting of the Association in August, 1901, describing a method of estimation of the total temperature expo sure of a plant. This method implied the use of thermographic curves, and the total heat exposures (temperature above zero centi grade, freezing point) and cold exposures (temperature below zero centigrade) were calculated in hour-degree units. Thus it was found that the flowers of the silver maple (Acer saccharinum) in the New York Botanical Garden were mature and ready for fertilization on March 26, 1901, after 1,100 hours exposure to air temperatures above the freezing point with a total heat exposure of 3,466.6 hour-centigrade-degree heat units. Draba vcrna (vernal whitlow grass) reached the same stage in 974 hours with 1,644 hour-centigrade-degree units of heat exposure. The above method of measuring the temperatures to which plants were exposed was applicable only to the thermometry of the air. The basal portion of the axis of a plant, often the larger part of its body, is imbedded in the soil, however, and no adequate study of the subject could be made until some graphic method was devised for obtaining continuous temperature records of the soil. The committee was given a second grant by the Associa- 125 126 tion, and by the aid of additional funds given by the New York Botanical Garden an effort was made to devise an instrument that would make such a record. The investigation was intrusted to the author, and he was so fortunate as to enlist the interest and secure the cooperation of Dr. Wm. Hallock, professor of physics in Columbia University, who undertook to devise a thermograph that would make a continuous record of the temperature of the soil at any depth desired. A paper by Prof. W. H. Bristol, " A new Recording Thermometer for closed Spaces " read before the Association at the Brooklyn meeting in 1894, furnished the FIG. 19. Hallock thermograph. A, bulb containing kerosene. B, heavy tube, soldered to polar opening in bulb. C, capillary tube connecting bulb, and expanding chamber. D, double expanding chamber. E, upright post with adjustment clamp at E, on expansion chamber and fastened to short lever arm at F. G, lever extend ing from axis, and bearing pen, which traces temperature record on the cylinder. H, adjustment to raise or lower pen in making corrections, and calibrations. K cylinder driven by internal clockwork which makes one revolution per week. The cylinder carries paper ruled horizontally to degrees centigrade. The rate of move ment carries the paper past the pen at such rate that two hours is taken to pass over the interval between two curved lines. Z, upright rod on hinged base to remove pen from contact with paper. M, base of cast iron. principle upon which the new instrument, which will be desig nated as the Hallock thermograph, was constructed. The essential features of the Hallock thermograph are as follows : The thermal element of the instrument consists of a cop per bulb or globe 11 cm. in diameter with a strengthening equato- 127 rial ridge, filled with commercial kerosene. A short section of copper tubing with a heavy wall is soldered to an opening in one pole of the globe, and the free end of the heavy tube receives a small copper tube with an external diameter of about 4 mm., a bore of one millimeter, and of any desired length. The tube is also filled with petroleum. The free end of the small tube is con nected with a chamber consisting of a pair of corrugated brass disks 8 cm. in diameter with the edges soldered together. The chamber is seated on a metal block fastened to the base of a re cording apparatus and the tube connects with the chamber through an opening in the metal block. An opening is made in the upper side of the first chamber and a second chamber of the same kind is soldered to it, the interior of the two chambers being thus connected (see Fig. 19, D). The pair of corrugated chambers are filled with petroleum as convenient during the course of construction, and care is taken to exclude all air from the bulb, tube and chambers. As the temperature in the bulb is made to rise it expands, and as both it and the small tube have fairly rigid walls, the total expansion of the liquid is made to press outwardly the walls of the chambers with corrugated walls, which expand and contract after the manner of a bellows. An upright post is fixed to the upper wall of the pair of cham bers, and it may be lengthened or shortened in making the nec essary adjustments. This post connects with a short arm 4 cm. in length at F, running to an axis held in bearings between two upright standards. A second arm 17 cm. long carrying a pen is attached to this axis extends to an upright record ing cylinder revolved by clockwork. The cylinder carries double ruled paper and occupies a week in a single revolution. The instrument is now adjusted so that the pen bears against the point on the paper indicative of the same temperature as that of the bulb as determined by a mercurial thermometer, and it is ready for use. At the end of a week the paper, bearing a con tinuous tracing of the temperature for that time, is removed and another put in its place. The peculiar usefulness of this apparatus lies in the fact that the bulb may be buried in the soil at some distance from the re- 128 corder, and a continued record made of the temperatures to which the roots of plants are subjected. The amount of liquid in the capillary tube and corrugated chambers is so small in comparison with that in the bulb, that the variations in volume of this por tion of the confined liquid make no practical differences in the readings. Thus no matter how warm the air might become, or even if the sun shone directly on the capillary tube the instru ment would show the temperature of the bulb to within a very small fraction of a degree, the error being so small as to be neg ligible in all ordinary experiments. This is further illustrated by the fact that the flame of a bunsen burner may be applied to this tube without apparent effect on the temperature shown by the indicator. But one of the Hallock thermographs has been constructed, and it has been installed as described below in a location in the FIG. 20. Meteorological station in Garden. Rain-gauge in corner of enclosure. The bulb of the Hallock thermograph is buried in the middle of the enclosure at a depth of 30 cm. The instrument shelter at the right contains the recording and registering apparatus. nurseries of the Garden, to which place all of the meteorological apparatus has been removed. The recording portion of the in strument, together with an air thermograph, has been placed in an instrument shelter of the United States Weather Bureau pattern. (See Fig. 20.) The capillary tube has been extended down through the floor of the shelter to the surface of the ground, being protected 129 from mechanical injury by being led through a groove in a board.

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