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automatic registration of changes in circumference taken up by a steel band in 1905, but I have been unable to find any description of results obtained. Such results would include the errors due to the high temperature coefficient of steel. Some measurements of expansions of trunks as solid columns were made by Trowbridge and Weil in 1918, but the most serious effort with accurate methods was that of Mallock in 1918, who used an arrangement including a tape of invar passed around the trunk and two superposed plates of glass by which changes in circumference caused displacements in interference bands of light. Direct and continuous observation yielded accurate results of value with regard to daily equalizing variations as well as of actual growth.

The trunk of a tree is largely composed of dead cells, but enclosing it is a thin sheet of spindle form cambium cells in 2 to 10 or more layers which in the growing season enlarge in thickness and divide lengthwise, those on the outside becoming transformed into phloem cells and those on the inner into wood cells or tracheids. Extending from the center of the trunk are thin sheets or rays of the medulla or pith of the young stem. The most recently formed cells of these elements are still living and in come trees the medullary cells remain alive for several years, so that the woody cylinder of the tree may comprise wood-cells or tracheids, vessels and thin-wall ray cells, some of which are alive. Externally to the cambium are sieve cells, bast fibers, etc., and cork cells, enclosed in a bark which varies widely as to structure in different species.

The greatest amount of increase or change in volume is that which results from the multiplication by fission of the cambium elements, and the following enlargement of the derivatives. The facts Jorge, Uruguay, from Jan. 12, 1885, to Jan. 12, 1890," Trans. Bot. Soc. Edinburg, 18: 456, 1891.

Friedrich, J., "Zuwachsautograph," Centralb. für das gasammte Forstwasen, 31. Nov., 1905, pp. 456–461.

5 Trowbridge and Weil, "The Coefficient of Expansion of Living Tree Trunks," Science, 48: 348, 350, 1918.

6

• Malloch, A., "Growth of Trees with a Note on Interference Bands Formed by Rays at Small Angles," Proc. Roy. Soc., 90, B, 186-191, 1918. Submitted Dec. 1, 1917.

7 Bailey, I. W., "Phenomena of Cell-division in the Cambium of Arborescent Gymnosperms and their Cytological Significance," Proc. Nat. Acad. Sc., 5: 283-285, 1919.

are not yet available for a definite determination of the part which growth in the phloem may play in the variations as recorded by the dendrograph. Much however is known as to the cytological program of the growing elements in cambium and phloem. A correlation of facts of this kind and of the seasonal changes in food supply will be necessary to interpret the "growth-impulses" lasting for a few days late in the season, displayed by many trees.

Dendrographic data, especially records of experimental settings, may be expected to afford further necessary corrections as to the time element in the interpretation of seasonal layers or "annual rings" upon which much reliance is placed as offering corroborative evidence as to climatic periods and solar cycles.

ILLUSTRATIONS.
PLATE I.

FIG. I. Earlier form of dendrograph which takes a bearing from a prepared area on the bark of the tree by one end of a small lever, the other end of which is connected with the short arm of a recording lever. An encircling belt of wooden blocks serves as a base and support. Flexible wire standards with a base of thin sheet metal are clamped in position on the wooden blocks and screw clamps which slide up and down on the wire standards serve to hold the floating frame in a horizontal position. The entire apparatus is so adjusted that a contact rod of the floating frame on the opposite side of the tree is held with gentle pressure against the tree and any variation in diameter is then expressed by movements in the lever set.

FIG. 2. Improved dendrograph lever set. A, inner end of quartz rod in contact with prepared surface on the bark of the tree. The outer end of the quartz rod is fitted with a metal guide which engages the short arm of the recording lever at B. The long arm of the recording lever D carries a pen which makes a tracing on ruled paper on a revolving drum. The horizontal member of the frame C which carries the recording lever may be toward or away from the tree to adjust the pen at any point on the paper record sheet.

8 Knudson, L., "Observations on the Inception, Season and Duration of Cambium Development in the American Larch (Larix laricina Du Roi Koch)," Bull. Torr. Bot. Club, 40: 271-293, June, 1913.

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Brown, H. P., "Growth Studies in Forest Trees. I. Pinus rigida Mill.," Bot. Gaz., 54: 386-402, 1912. "II. Pinus strobus L.," ibid., 59: 198-240, 1915. Bailey, I. W., Phenomena of Cell-division in the Cambium of Arborescent Gymnosperms and their Cytological Significance," Proc. Nat. Acad. Sci., 5: 283-285, 1919. "The Cambium and Its Derivative Tissues. II. Size variations of Cambium Initials in Gymnosperms and Angiosperms," Amer. Jour. Bot., 7: 355-367, 1920. "II. A Reconnaissance of Cytological Phenomena," Amer. Jour. Bot., 7: 417-434, 1920.

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THE ACTION OF BASES AND SALTS ON BIOCOLLOIDS

AND CELL-MASSES.

BY D. T. MACDOUGAL.

(Read April 21, 1921.)

The suggestion was made in an earlier paper that the common metals which enter into nutrient solutions might find their chief importance in restricting, limiting or defining hydration of the cellcolloids.1 MacDougal and Spoehr carried out a series of tests upon this matter and found in fact that the strong metallic bases when used at concentrations of 0.01 N do limit or restrict the hydration of agar according to their place in the electromotive series, the least swelling taking place under the action of the strongest base, with rubidium unplaced. Beginning with the strongest the series runs K(Rb) NaLi, and if calcium were added to the series the swelling under its action was less than that in potassium.2

When the concentrations were reduced however to 0.001 N it was found that hydroxides of all of the metals increased the hydration capacity of agar. This was of importance as a review of all of the available data seems to show that the range of the H+-OH- balance in the plant cell lies between the values expressed by Рнз and PH II, or between about 0.01 M aspartic, succinic or propionic acid and under o.001 N KOH.

The reversal of effects at great attenuations in the hydroxides. led to the extension of auxographic measurements upon the effects of low concentrations of the salts which are of such interest and importance in cultures, and the action of chlorides, nitrates and sulfates of potassium, calcium, sodium and magnesium upon agar, gelatine and mixtures was made at Carmel in the summer of 1920. 1 MacDougal, D. T., "Growth in Organisms," Science, 49: 599-605, 1919. (See page 1 of reprint.)

2 MacDougal, D. T., and H. A. Spoehr, “The Components and Colloidal Behavior of Plant Protoplasm," Proc. Amer. Phil. Soc., 59: 154, No. 1, 1920.

PROC. AMER. PHIL. SOC., VOL. LX, B, JULY 25, 1921.

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