RATE OF CUEM FORMATION IN BROMUS INERMIS 
By L. R. Waldron 
Plant Breeder , North Dakota Agricultural Experiment Station 
INTRODUCTION 
Various investigators have made growth studies upon different organ¬ 
isms. Working with the rat, Donaldson 1 and other workers have 
published a number of formulas showing the growth of certain organs 
with respect mainly to the growth in body weight. The curves are 
mostly logarithmic in type. They are based on careful data and show 
the general trend of organic development relative to size of animal. 
Pearl has made studies in growth phenomena and has developed 
curves to express the general type of growth. Working with Cerato- 
phyllum, 2 he developed a logarithmic curve of the general type 
log (x-a) 
which furnished a symbolical expression of the manner of growth dealing 
with rate of increase of leaves per whorl along the axis of the plant. 
He says: 
The mean number of leaves per whorl increases with each successive whorl, and 
in such a way that not only does the absolute increment diminish, but also the rate 
of increase diminishes as the ordinal number of the whorl measured from a fixed 
point increases. 
In other words, this phase of growth is rather rapid at first and then 
slows down, both absolutely and comparatively. 
Working with maize, Pearl and Surface 3 secured data upon height of 
plant which, from their previous studies, they were confident could be 
fitted with a logarithmic curve, probably of the type 
Y = A +B log x. 
Here again the growth movement is rapid at first, but this rapidity 
decreases later. Pearl goes so far as to state that the growth of an 
organism can usually, if not always, be described by a curve of this 
type. 
1 Donaldson, Henry H. the rat. reference tables and data for the albino rat (mus nor- 
vegicus albinus) and the Norway rat (mus norvegicus). 278 p., 31 charts, 89 tab. Philadelphia, 
1915. References to the literature, p. 214-267, and references at end of chapters. Mem. Wistar Inst. 
Anat. and Biol., no. 6. 
2 Pearl, Raymond, variation and differentiation in cEratophyllum. 136 p. f 26 fig., 2 pi. 
Washington, D. C., 1907. Literature cited, p. 135-136. Carnegie Inst. Wash., Pub. 58. 
* Pearl, Raymond, and Surface, Frank M. growth and variation in maize. In Ztschr. Indukt. 
Abstam. u. Vererb., Bd. 14, Heft 3/4, p. 97-203, 15 fig. 1915. Bibliography, p. 171-172. Preliminary 
abstract in Proc. Nat. Acad. Sci., v. 1, no. 4, p. 222-226. 
Journal of Agricultural Research, 
Washington, D. C. 
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(803) 
Vol. XXI, No. 11 
Sept. 1,1921 
Key No. N. Dak.-x 
