Not all forest trees begin to grow at the same time.

Some start early in spring while others begin rather late. The Wild Black Cherry Prunus serotina is the first forest tree in the vicinity of Mont Alto to begin height growth. The elongation of its twigs starts about the fourth of April. The Domestic Cherry, Prunus Avium, begins its growth about four days later than the native Wild Black Cherry. The Sweet Buckeye, Aesculus octandra, begins about April 6th, White Pine, Pinus Strobus, about April 18th, Tulip Tree, Liriodendron Tulipifera, about April 25th, and Norway Spruce, Picea Abies, about May 6th. The date when the different species start the elongation of their twigs depends upon the inherent tendency of the species and the factors of the environment. The late opening of the buds of Norway Spruce is not a local characteristic, but an inherent tendency, for records from Germany show that they usually open after May 8th, and in the extreme northern part after the end of May. On the other hand, factors of the environment, such as latitude, altitude, exposure, shade, and shelter, also have a strong influence on the starting time of the season's growth. As a rule, buds open about 21⁄2 to 3 days later with each degree of latitude and about 2 to 21⁄2 days later with each 350 feet of altitude. White Oak begins its growth from 7 to 14 days later on northern than on southern exposures on the Mont Alto State Forest. Trees with small and partially or completely imbedded buds such as Honey Locust, Black Locust, Kentucky CoffeeTree, Tree of Heaven, and Catalpa, begin growth relatively late. Nature seems to protect the

late frosts, for the small and deeply imbedded buds are not stimulated so early in spring as large exposed buds; hence, the resultant vegetative growth usually appears after the damaging frost period.

Pennsylvania is the meeting ground of many northern and southern forest tree species. The northern follow the mountains towards the South and the southern extend northward through the valleys. The distinctly southern species, which are decidedly sensitive to spring frosts, as a rule, begin the elongation of their shoots rather late, that is, after the danger period of frost damage is past. The Eastern Catalpa, supposedly a native of the South Atlantic States, does not leaf out until the latter part of May. Likewise other southern species, such as Persimmon, Kentucky Coffee-Tree, and Bald Cypress postpone the beginning of their vegetative elongation until late spring.

The range of the period during which the height growth of forest trees ceases is longer than that during which height growth starts in the spring. The Sweet Buckeye, Aesculus octandra, usually completes its growth at Mont Alto as early as May 10th to May 15th, and by June 15th one can find full-sized winter buds. This species is the first to complete its height growth of the season. Most species of forest trees in southern Pennsylvania cease growing during the latter part of May and the early part of June. Only a few species continue their growth into July. On June 10, 1919, I examined 79 different species of trees in the vicinity of Mont Alto, 55 of which, that is 70 per cent., had already ceased growing in height. On June 18 and 19,

1919, I examined 50 species of trees in the vicinity of Bedford, Pa., and found that the height growth of 40 had already stopped. This is an unusually high percentage of growth cessation, and is probably due to the extremely cold period during the early part of May, followed immediately by an unusually hot period during late May and early June. Such extreme temperatures and the abrupt transition from one extreme to the other are potent factors in retarding growth and in extreme cases may cause entire cessation of growth. The White Pine, which usually stops growing in the vicinity of Mont Alto about June 15th, but may continue to grow as late as June 30th, ceased growing this year (1919) about June 3rd. It is the writer's belief that 85 per cent. of the forest trees of Pennsylvania have already (June 20, 1919) completed their normal height growth for the season. Of the remaining 15 per cent, the Tulip Tree, Sycamore, and the Larches are prominent species, which may continue to grow until the middle or latter part of July. By the first of August the normal height growth of all the forest trees of Pennsylvania has, as a rule, ceased.

In order to determine the progress of the height growth each species must be examined by itself, for each individual species possesses distinctive inherent growth characteristics. Some place their growth without a break, while others place it by leaps and bounds alternating with rest periods. In this respect the method of working followed by trees, and growth surely is work, differs little from the methods of other organisms, including man. Rarely does any organism work continuously, but rest periods are usually, and sometimes frequently, interspersed between the periods of work. Rest periods, however, should not be regarded as synonymous with idleness, for they are normal prerequisites to the optimum functioning of all organisms. Without them no organism can attain optimum efficiency nor maintain health.

Few comprehensive statements can be made regarding the growth behavior of forest trees during the growing season. There is a wide divergence between the height growth behavior of Wild Black Cherry, Sweet Buckeye, White Pine, Tulip Tree, and Norway Spruce. Yet, in spite of this wide divergence the fundamental features of the growth procedure throughout the growing season may be summarized as follows: Growth begins slowly, after a variable period rises rapidly, then reaches a maximum which is maintained for a short while, finally falls gradually to a minimum, and then ceases completely.

The actual growth is, however, less regular, for the rate of growth usually exhibits a certain rhythm or periodicity. It progresses by leaps and bounds alternating with rest periods, which may be of long or short duration. Rest periods of short duration occur frequently and at irregular intervals, but are hard to detect with instruments of ordinary precision. Rest periods of longer duration are also common and readily measurable.

The terminal shoot of a Chestnut Oak, Quercus Prinus, started to grow on April 17, 1918, and continued its elongation until May 23rd, when the first upward thrust ceased. A resting period of 24 days followed and on June 16th growth was again resumed and continued until July 13th, a period of 27 days. The first growing period extended over 36 days during which the terminal shoot elongated a total of 10 inches, that is an average of approximately one-third of an inch per day. This was followed by a cessation of growth for 24 days when the second and final elongation of the season began. The second growing period extended over only 27 days during which the terminal shoot elongated a total of 13.5 inches, that is an average of onehalf an inch per day. Such a periodicity of growth is not unusual, but rather peculiar to certain species. Pin Oak, Black Oak, Chestnut Oak, and Pitch Pine frequently begin to place a second growth 10 to 25 days after the original growth of the season has ceased.

The period during spring and summer when height growth does not progress may be regarded as a resting period, a recuperative period, or a period of preparation. The trees apparently rest but in reality they are preparing for the next upward thrust which may be longer than the original advance. Furthermore, the writer believes that the recurring rest periods may become a rather fixed and regular feature of the growth of certain species. This is certainly true in the case of normal young Pitch Pine in the vicinity of Mont Alto which exhibits annually a cessation of growth for a period of 2 to 3 weeks.

The rate of tree growth not only fluctuates throughout the growing season but also during each day. The maximum growth usually occurs late at night, apparently after the preparation and translocation of food and other essential materials becomes less active, and the minimum growth falls in the afternoon of each clear day when the greatest activity in the manufacture of starch and sugar is in operation.

About 20 trees of each of the four species

The foregoing tabulation shows that trees grow about twice as much at night as during the day. By using instruments of greater precision the percentages would, no doubt, be changed somewhat, but the general comparative rate of growth would still stand unchanged.

To some persons it may appear that the problem of growth behavior of trees has only an academic application. This point of view is, however, untenable for there is an economic side to the study. If conducted in a scientific manner it will supply the basic data for the preparation of a rational schedule for transplanting in the nursery and setting out trees in the woodlot and forest. Foresters, silviculturists, and plant physiologists recommend that planting and transplanting operations should be conducted when the material to be planted is in a dormant condition. No fault can be found with their recommendation, but in order to execute it properly one must know when trees really are dormant. This can be ascertained best by determining when trees grow, since growth is so evident and measurable, and whenever trees are not growing they are dormant, that is, in a static condition, the duration of which is hard to determine.

Furthermore, such a study facilitates the preparation of a schedule for field work covering the problem of growth. That determination of the quantitative and qualitative growth on cut-over lands is one of the most important and urgent problems in American forestry is conceded by the most authoritative foresters. This is one of the four major problems which the Chairman of the Forestry Committee in the Division of Biology and Agriculture of the National Research Council recommends as worthy of immediate and thorough consideration. Heretofore, we have generally been instructed that the height growth of the season cannot be accurately ascertained until late in fall or during the winter months when the weather is relatively

unfavorable for field work and the days rather short. Consequently it now follows that since trees actually cease growing in height in May or June, no reasonable exceptions can henceforth be filed against the collection of height growth data immediately after the cessation of growth in summer.

It should be understood, however, that the problem WHEN TREES GROW is but a prelude to the major problem, which is far more comprehensive, and includes also a study of diameter and volume of growth of the stem and the growth of roots, all of which should be undertaken; for the results derived therefrom would be of great economic value.

A knowledge of WHEN TREES GROW also aids in the determination of the best time to peel bark. Bark can be peeled satisfactorily only when the sap is abundant and active. Briefly, the bark peeling season coincides with the growing season of trees, even to the extent that lumbermen recognize a "second sap" period during June in Chestnut Oak trees. This furnishes practical proof that the second period of growth recurs rather regularly in this species. The second period is usually short and the bark does not peel so satisfactorily as in the first period of the season. It is, therefore, recommendable that the period of active growth be accurately determined for each species, the bark of which is peeled, in order to determine the exact limits of bark peeling season.

A thorough study of the growth of trees will also furnish much needed information to the legal profession. Many legal decisions concerning boundaries and titles hinge on the question whether each growth ring represents the growth of one season, or if fictitious rings are sometimes formed. The writer examined a large number of Pitch Pine and Chestnut Oak trees and found that fictitious rings are regularly formed when a prolonged resting period occurs within the growing season. Hence, in some cases two rings represent the growth of a season, instead of one annual ring.

I wish to add that the problem-WHEN TREES GROW-is not only of technical interest and economic value but might be used as a means of developing real tree appreciation among the children of our public schools. The best soil in which to plant love for trees is the heart of childhood and womanhood. The present lack of a fuller appreciation and a more compelling warmth towards the out-of-doors in which we daily move and often toil is largely due to the kind of education practiced in the past and still

retained in a few ultra-conservative communities. It is pedagogically criminal to instruct the boys and girls in Pennsylvania concerning the Eucalyptus trees of Australia, the Big Trees of California, the Yew trees of England, and the Cypress trees of the South without mentioning the White Oak, Chestnut, Tulip Tree, or White Pine which may stand near the school-house door. And merely to mention the names of these trees is not sufficient. This simply serves as an introduction, but if the children are also instructed concerning their growth and other activities they begin really to know these trees, and will continue to observe and study their habits,

I regret that a certain geography used extensively in the public schools of our State is often recommended highly because is contains a special feature of fourteen pages in the rear part pertaining especially to the geography of Pennsylvania. In this special part the subject of plant life is omitted entirely and animal life is considered in a space of eight lines. In the general part of this textbook the plant and animal life of distant Africa are considered in eleven and twenty-three lines respectively. More than four times the space is devoted to the consideration of the animals and plants of far away Africa than to the home fauna and flora with which the children come in contact every day.

J. S. ILLICK,

Chief, Division of Silviculture, Pennsylvania Department of Forestry.

Pennsylvania Forestry Legislation.

T

HE Legislature of Pennsylvania adjourned on June 26, 1919, and the following proposed forestry laws were not passed: An act establishing a Conservation Department to be composed of the Department of Forestry, Department of Fisheries, Board of Game Commissioners and the Water Supply Commission.

The act sponsored by the State Grange proposing changes in the Department of Forestry. The revised and improved Forest Protection Code.

The forestry bills approved by the Governor and which are now laws are:

Act 61-Makes all lands acquired for State Forests subject to an annual charge of one cent per acre to be paid to the counties in which the State Forests are located.

Act 293-The act establishing the Department of Forestry was amended, making a State Forest Commission, composed of the Commission of

Forestry and four other members appointed by the Governor. This Commission is given additional power in that it can acquire land for State Forests by condemnation proceedings, appoint scientific assistants and other employes; also publish the results of forestal investigations and inquiries. The salaries of the Commissioner of Forestry and of the Deputy Commissioner of Forestry are raised.

Senate Act 733-Provides for condemnation by the Commonwealth of lands suitable and desirable for forestry purposes when a price for such lands cannot be found, and defines the powers and duties of the Department of Forestry or the Department of Conservation in relation thereto.

The General Appropriation Bill giving $919,200 for the use of the Forestry Department for two years was reduced to $899,200, $10,000 being cut from the labor fund and $10,000 from the Forest Protection Fund.

Forests of British Columbia.

The Commission of Conservation of Canada has just issued a comprehensive report by H. N. Whitford and Roland D. Craig, on the "Forests of British Columbia."

This report states that the timber on 100,000 square miles, or two-thirds of the land once forested has been totally destroyed by fire, and on over half of the remaining 55,855 square miles the timber has been seriously damaged. Using the timber still standing as a basis, it is estimated that the province has lost through forest fires at least 665 billion feet board measure.

It is thought that on the remaining timber land about 28,000 square miles carry at least 5,000 to 8,000 b. f. per acre, and 23,800 square miles between 1,000 and 5,000 b. f. per acre. The principal trees are the Western red cedar, Douglas fir, Spruce, Western Hemlock, and Balsam which comprise over 92 per cent. of the standing timber. The total stand of all kinds of merchantable timber is estimated as 350 billion board feet of timber. The cut of the Province for the last five years has averaged 14 billion board feet.

With over 100,000 square miles on which young forests are established, and which if protected it is estimated should produce from 5 to 7 billion board feet per annum, the forest resources of British Columbia could, under conservative exploitation, supply at least five times the present cut, without seriously depleting the capital stock.