CHAPTER III THE RATE OF GROWTH

We can demonstrate the fact, however, in the case of man by the help of certain very interesting measurements which have been recorded by Daffner⁶⁷, of the height of German cadets, measured at half-yearly intervals.

Growth in height of German military Cadets, in half-yearly periods. ( Daffner. )
	Height in cent.	Increment in cm.
Number observed	Age	October	April	October	Winter ô§-year	Summer ô§-year	Year
12	11ã12	139ôñ4	141ôñ0	143ôñ3	1ôñ6	2ôñ3	3ôñ9
80	12ã13	143ôñ0	144ôñ5	147ôñ4	1ôñ5	2ôñ9	4ôñ4
146	13ã14	147ôñ5	149ôñ5	152ôñ5	2ôñ0	3ôñ0	5ôñ0
162	14ã15	152ôñ2	155ôñ0	158ôñ5	2ôñ5	3ôñ5	6ôñ0
162	15ã16	158ôñ5	160ôñ8	163ôñ8	2ôñ3	3ôñ0	5ôñ3
150	16ã17	163ôñ5	165ôñ4	167ôñ7	1ôñ9	2ôñ3	4ôñ2
82	17ã18	167ôñ7	168ôñ9	170ôñ4	1ôñ2	1ôñ5	2ôñ7
22	18ã19	169ôñ8	170ôñ6	171ôñ5	0ôñ8	0ôñ9	1ôñ7
6	19ã20	170ôñ7	171ôñ1	171ôñ5	0ôñ4	0ôñ4	0ôñ8

In the accompanying diagram (Fig. 30) the half-yearly increments are set forth, from the above table, and it will be seen that they form two even and entirely separate series. The curve joining up each series of points is an acceleration-curve; and the comparison of the two curves gives a clear view of the relative rates of growth during winter and summer, and the fluctuation which these velocities undergo during the years in question. The dotted line represents, apôÙproxôÙiôÙmateôÙly, the acceleration-curve in its continuous fluctuation of alternate seasonal decrease and increase.

In the case of trees, the seasonal fluctuations of growth⁶⁸ admit {119} of easy determination, and it is a point of considerable interest to compare the phenomenon in evergreen and in deciduous trees. I

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