No. 1, August, 1921] HORTICULTURE 45 



coefficient for the path from A to X is defined as the ratio of the standard deviation of X 

 due to A divided by the total standard deviation of X. 



Px.A = 



The deviation of X directly caused by a unit deviation of A is 



Px.A 



("a "a 



The coefficient of determination of X hy A, 'dX.A' measures the fraction of complete deter- 

 mination for which factor A is directly responsible in a given system of factors. — These for- 

 mulae are developed and illustrated for systems of independent causes, chains of causes, 

 non-additive factors, non-linear relations, effects of common causes and systems of correlated 

 causes. Their relation to multiple correlation is shown and general formulae are developed. 

 Illustrative material is given on birth weight of guinea-pigs and on transpiration of plants. — ■ 

 John W. Gowen. 



HORTICULTURE 



J. H. GouRLEY, Editor 

 H. E. Knowlton, Assistant Editor 



FRUITS AND GENERAL HORTICULTURE 



(See also in this issue Entries 3, 12, 15, 30, 40, 47, 48, 50, 57, 69, 76, 78, 160, 221, 242, 255, 

 263, 339, 415, 425, 428, 430, 432, 434, 435, 444, 445, 446, 447, 465, 498, 524, 530, 552) 



281. Anonymous. [Rev. of: Fletcher, S. W. The strawberry in North America: 

 history, origin, botany, and breeding, xiv -f- 234 V- Macmillan Co.: New York, 1917.] Sci. 

 Prog. [London] 14: 350. 1919. 



282. Ballou, F. H. An orchard tragedy. Monthly Bull. Ohio Agric. Exp. Sta. 6: 9- 

 11. Fig. 1-2. 1921. — The article contains a discussion concerning tillage-cover-crop versus 

 grass mulch practice in a hillside orchard as based upon tests upon hilly land in southern Ohio. 

 In spite of careful cultural work the tillage-cover-crop section was in deplorable condition 

 at the end of the test. Orchardists are adopting the mulching method because it results in 

 equally generous fruit production, is less expensive, less difficult, and less dangerous. — R. 

 C. Thomas. 



283. Ballou, F. H. Ensee apple. An Ohio variety coming into prominence. Monthly 

 Bull. Ohio Agric. Exp. Sta. 6: 12-13. 1921. — Origin, similarity to the Rome Beauty, and mer- 

 its of the Ensee apple are discussed. — R. C. Thomas. 



284. Brown, G. G. The orchard-fertility problem. Agric. Jour. [British Columbia] 

 S: 326, 354-355; 6: 20-21. 1921. — This report summarizes the results of orchard fertilizer ex- 

 periments in other stations and compares them with results obtained by the Oregon Agricul- 

 tural experiment station. Special emphasis is placed upon the use of alfalfa as a permanent 

 shade crop and the effect of chemical manures, especially nitrate, on the growth of alfalfa. 

 It emphasises the fact that legumes used as cover crops do not need added nitrogen, but rather 

 are harmed by it; and that the growing of a legume, with possibly the addition of some acid 

 phosphate and potash, may prove to be a good system for maintaining orchard fertility. — 

 A. F. Barss. 



285. H., T. A. [Rev. of: Newland, H. Osmun. The planting, cultivation and expression 

 of cocoanuts, kernels, cocoa, and edible vegetable oils and seeds of commerce. A practical 

 handbook for planters, financiers, scientists and others, vi + 111 p., 11 pi. Charles Griffin 



