i9i i.] Summary of Agricultural Experiments. 935 



the leaf buds and a larger percentage of nitrogen and potash in the 

 dry matter, but a smaller percentage of lime, phosphoric acid, and ash. 



The experiments during 1909 were also conducted with a view to 

 ascertaining whether the substances in the leaf return into the tree in 

 the autumn before the fall of the leaf. Conclusive evidence was 

 obtained in support of this view in the case of nitrogen and phosphoric 

 acid. While the amounts of these substances in the leaf remained 

 fairly constant up to the penultimate analysis, a marked decrease was 

 shown in the period between the penultimate and the last analysis, the 

 last analysis being made at the end of October or at the beginning of 

 November, when the leaves came away easily from the tree at a touch. 

 The decrease in the amount of dry matter during the last stage of the 

 experiments was also most noticeable (except in the case of plums), and 

 decreases were the rule during the last period with potash and lime. 

 This return of material from the leaf into the tree appears, however, 

 to be dependent upon the weather. Such a return will take place if 

 summer conditions extend far into autumn, while if cold weather occurs 

 early the leaves fall too soon to admit of this return taking place.. 



Use of Formalin for Smut (Praktische Blatter fur Pflanzenbau und 

 Pflanzenschutz, November, 19 10). — Experiments with regard to the 

 treatment of the seed of cereals with formalin for the prevention of smut 

 have been carried out during the last ten years by Professor Jaczewski, 

 at the Russian Agricultural Phytopathological Institute, and the follow- 

 ing recommendations are made as a result of his experiences in this 

 direction. 



The seed should not be too old. The older the seed, the more 

 easily does it absorb the formalin solution, and the germinating capacity 

 is liable to be injured by the formalin reaching the germ. 



The formalin solution should preferably be weak, say, 0*15 per cent., 

 or one pint of 40 per cent, formalin to 38 gallons of water. This 

 solution is practically identical with that recommended in the Board's 

 Leaflet, No. 92, viz., one pint of formalin to 36 gallons of water. 



The seed should not be left to steep for too long a time, but Prof. 

 Jaczewski regards a period of about two hours as most suitable for 

 disinfection, and states that this will not injure germinating capacity. 

 A period of ten minutes is suggested as sufficient in the Board's leaflet. 

 The treatment by immersion is somewhat inconvenient, however, and 

 a better method is to collect the seed in heaps, and spray with the 

 above solution, each heap being turned, so that all the seed receives 

 treatment. When this is complete, the seed should be covered over, 

 left for two hours, and then spread out to dry. Further particulars of 

 this method will be found in the leaflet already referred to. 



Experiments on this subject have also been mentioned at some 

 length in this Journal, Vol. IX., p. 366, Vol. XL, p. 214, and Vol. XII. , 

 p. 289. 



Time of Harvesting Peppermint for the Production of Oil. — The 

 most important stage in the cultivation of plants grown for the pro- 

 duction of volatile oils, such as peppermint, is probably the harvesting 

 of the crop. In order to determine at what stage of development the 

 amount of odorous constituents of the plant is at its maximum, both 

 as regards quantity and quality, and thus to decide at what period the 



