796 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



yield may not be equal to the cost of the nitrogen applied. And it is 

 shown in the experiments conducted with nitrate of soda, on different 

 crops, that in the case of grain and forage crops, which utilised the nitrate 

 quite as completely as the market-garden crops, the increased value of 

 crop, due to nitrate, does not in any case exceed $14 per acre, or a money 

 return at the rate of $8.50 per 100 lb. of nitrate used ; while in the 

 case of the market-garden crops the value of the increased yield reaches, 

 in the case of one crop, the high figure of over $263 per acre, or at 

 the rate of about $66 per 100 lb. of nitrate. Where the increase in yield 

 will more than pay the cost of application, it cannot be too strongly 

 urged upon the attention of farmers : 



1. That the constituents, nitrogen, phosphoric acid, and potash, as found 

 in commercial supplies furnishing these elements, do serve as plant food, 

 nourishing the plant in the same manner as those in home manures, and 

 should therefore be liberally used in order to guarantee maximum 

 crops. 



2. Of these constituent elements nitrogen is of especial importance, 

 because it is the one element which, in its natural state, must be changed 

 in form before it can be used by the plants. Hence, its application in an 

 immediately applicable form is especially advantageous for quick-growing 

 vegetable crops, whose marketable quality is measured by rapid and 

 continuous growth, and for those field crops which make their greatest 

 development in spring, before the conditions are favourable for the 

 change of the nitrogen in the soil into forms usable by plants. — F. A. W. 



Fig* Trees on Walls out of Doors. By H. W. Ward (Gard. 

 Chron. No. 891, p. 49 ; Jan. 23, 1904). — The author in this paper 

 gives very clear directions for the cultivation of Fig trees in the above 

 position. The article is divided under three headings : The selection of 

 varieties ; the rooting medium ; training and pruning. — G. S. S. 



Flora of Europe, New Members of the. By Dr. F. Hock (Beih. 

 Hot. Cent, xviii. Abt. ii. pp. 79-112). — Finishes this series of papers with 

 a complete list of the 627 species noted as escapes and emigrants in 

 middle Europe : of these at least fifty have established themselves during 

 the fifty years of observation, which is one species a year. Of these 

 fifty, some thirty species are North American, twelve Mediterranean, 

 four from South and East Asia, three from South America, and one 

 from tropical Africa. No south temperate (Australian, New Zealand, 

 or Cape Colony) plant has established itself, though a considerable 

 number occur in the 627 listed. The author points out that commercial 

 intercourse has a very strong influence, most being found near Ham- 

 burg, Berlin, and seaports or centres of population ; most are apparently 

 accidentally introduced in wool or corn or other seeds. At the same time 

 the percentage of observing botanists increases with the population, and 

 this has an important bearing on the question as shown by the case of 

 Straasburg, where Ludwig has during the last year found many. 



The inability of the south temperate plants to establish themselves is 

 ascribed to their not being fit to stand the strain of European com- 

 petition. 



