1 



522 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



" This is the way stable manure and green manures act. This is the f 

 principal office of nitrate of soda, potash, and phosphoric acid." 'j 



It will not be thought surprising that Dr. Hopkins protested ! 

 vigorously against the circulation of such ideas. Dr. Davenport points j 

 out that "the logical conclusion of this theory of the Bureau of Soils 

 is that in practical farming operations all matters of fertility may be 

 neglected, provided only the proper rotations be maintained." j 



It is not perhaps advisable to enter further into the controversial 

 part of these papers. It is interesting to find that Sir Humphry 

 Davy in 1839 mentions supposed excretions from roots " injurious to 

 the plants which have yielded them and yet beneficial to other kinds of 

 plants." 



But, as Dr. Hopkins shows, there is a limit to the absolute total of I 

 plant food in all soils. The average prairie soil of more than twenty' 

 counties in Illinois contains so limited a supply of phosphorus that sixty 

 years of the best crops would require every pound of it (to a depth of 

 one foot). 



A.lthough it has long been known that soluble materials are brought 

 up from the subsoil by capillary moisture, yet there is no question 

 that the drainage water removes large amounts of plant food. From 

 75 to 90 per cent, of the original rock formation (in limestone soils) is 

 not infrequently removed by leaching. Dr. Hopkins also shows that 

 Professor Whitney's theories are not borne out by the results of the 

 Eothamsted experiments (in which he is supported by Dr. Hall). The 

 official Agricultural Chemists' Association appointed a committee of 

 seven to examine the subject. Six out of the seven uphold Dr. Hopkins 

 both in his criticism of Professor Whitney's data and in his protest 

 against the teaching of such views to practical farmers. — G. F. S.-E. 



Sphagfnum fOP Cutting's. By A. van der Heede {Le Jard., 

 vol. xxiv.. No. 552, p. 59; Feb. 20, 1910).— Cuttings strike 

 well in a bed of fresh sphagnum 25-60 cm. deep. If kept moist by ) 

 wetting the bottom of the moss, the temperature being from 15-20^ 0., 

 roots will be thrown out in a few days — four to five for Coleus, eight to 

 fifteen for Heliotrope, two to three for Alternanthera, and about a fort- 

 night for Fuchsias. As soon as the roots appear the cuttings may be 

 potted in a light soil, rendered porous by the use of white sand. ' 



F. A. W. 



Spraying". Ed. by Frederic Cranefield (U.S.A. St. Hort. Soc. 

 Wisconsin, Bull. 19; April 1910; 15 figs.). — This bulletin contains 

 excellent formulae for insecticides and fungicides compiled from 

 various sources, and illustrations of spraying machines and pumps. 



V. G. J. 



Spraying- with Arsenate of Lead. By H. M. Ashby [Ann. 

 Rep. Wisconsin State Hort. Soc. 1909, vol. xxxix. p. 157). — Points out 

 the advantages of this spray as compared with Paris green for exten- 

 sive use: (1) it settles more slowlv ; (2) it is less likely to burn foliage. 



E. A. B. 



