GROWTH AND DEVELOPMENT. 75 



of their age. As far as could be observed the growth proceeds equally slowly during the fifth and 

 sixth years, the plant at the end of that period being from 5 to 7 or 7J inches in length. 



Stage of rapid growth. — With its seventh year the tree may be said to enter on its most 

 vigorous growth. Henceforth the stem (primary axis) increases rapidly in length, and the 

 development of branches (lateral axes) proceeds at an equal rate in regular whorls, to which the 

 symmetry of the tree in that stage of its development is due. During the seventh year, generally, 

 the tree doubles its length, and during a number of successive years the rate of growth in that 

 direction varies between 10 and 20 inches annually, as is clearly shown by the length of the 

 internodes separating the whorls. As the branches increase in length they produce, in the same 

 order mostly, two opposite secondary branches. With the rapid expansion of the leaf surface, 

 the formation of wood keeps pace. The rate of growth in diameter, as well as in height, during 

 this period is, of course, variable according to differences in the physical condition of the soil, as 

 well as in the available amount of plant food and moisture it contains, and no less upon differences 

 in temperature and of exposure to light and air. 



When the tree has reached its second decade it begins to x>roduce flowers and fruit. Having 

 during the course of the following fifteen years reached a length of from 40 to 45 feet, with the 

 main stem clear of limbs, the growth of branches does not proceed with the same regulaiity; 

 consequently they are no longer arranged in regular whorls, but appear irregularly, and thus the 

 symmetry of the tree is lost. 



Stage of slow growth. — Eapid as is the increase in length of the primary axis or trunk, amount- 

 ing during the first half century, in the average, to 14 or 13 inches annually, the rate is subse- 

 quently greatly diminished, averaging from the fiftieth to about the one hundred and fifteenth 

 year but from 4 to 5 inches, and from this time to the age of two hundred and fifty years only 1£ 

 inches— that is, at a relative rate of 10, 3, and 1 in the three successive periods. The decrease in 

 the accretion of wood corresponds with the reduction in the growth of the branches and conse- 

 quent reduction of foliage. From what has been said, it is seen that the longleaf pine attains 

 maturity of growth, with the best qualities of its timber, at an age of from one hundred and eighty 

 to two hundred years. After having passed the second century the trees are found frequently to 

 be wind shaken and otherwise defective. The deterioration of the weather beaten crown lessens 

 the vitality of the tree, and the soil, under prevailing conditions, becomes less and less favorable. 

 In consequence, the trees become liable to disease and mostly fall prey to the attacks of parasitic 

 fungi (red heart). Instances of trees which have reached the maximum age of two hundred and 

 seventy-five or three hundred years are exceptional. 



In order to ascertain the age required to furnish merchantable timber of first quality, meas- 

 urements were made of a number of logs in a log camp in the rolling pine uplands of the lower 

 division of the coastal pine belt near Lumberton, Washington County, Ala. From the results 

 obtained it appears that in this section of the eastern Gulf region, at the lowest figure, two 

 hundred years are requisite to produce logs of the dimensions at present cut at the sawmills. 



Demands upon soil and climate. — In its demands upon the soil this pine is to be counted among 

 the most frugal, as far as mineral constituents, which are considered as plant food, are concerned, 

 if only the mechanical conditions which influence favorable soil moisture are not wanting. It 

 thrives best on a light siliceous soil, loamy sand or pebbles or light sandy loam, with a slightly 

 clayey subsoil sufficiently porous to insure at least a partial underdrainage and to permit unim- 

 peded development of the long taproot. Whenever the tree meets an obstacle to the development 

 of this root it remains more or less stunted. 



The luxuriance of the growth and increase in size of the timber, however, is greatly influ- 

 enced by the quantity of clay present, particularly in the deep subsoil, which improves mechanical 

 and moisture conditions. This is strikingly exhibited in the timber of the level pine flats west of 

 the Mississippi Eiver, although the surface drainage is almost wanting and the underdrainage 

 through the loamy strata slow, so that the surface of the soil remains damp or water-soaked for 

 the greater part of the year ) the stand of timber of first-class dimensions exceeds considerably 

 that of the rolling pine uplands on the Atlantic slope and the lower part of the pine belt in the 

 eastern Gulf region, which are poorer in clay. Evidently, although the underdrainage is less 

 perfect, the moisture conditions during the dry season of the year, the time of most active growth, 

 must be most favorable, The same fact is apparent in the upper part of the coast pine belt in 



