It seems probable that all the experimental work that has been discussed will prove to be simply preliminary to a far greater practical application of the principle of stimulation or increased growth. While the physiologists have been feeling their way towards the conclusions put forth on this subject, the agriculturists have been discovering and extending the application of artificial manures, until at the present time such manuring is coming into its own and is receiving more of the widespread attention that it deserves. The possibility now exists that in some respects the two lines of work are converging and that the more purely scientific line will have a big contribution to make to the strictly practical line. Artificial manuring aims at improvement of the soil and crop by the addition of food substances that are needed in a particular soil, a result that used to be obtainable only by the use of the bulky farmyard manure, seaweed, &c. Apart from any other aspect of the matter the artificials, when intelligently used, are far more easy to handle and to regulate in supply, and they yield excellent results, especially in conjunction with a certain proportion of organic manures. The further prospect now opened up is the possibility of utilising some of these stimulating compounds as artificial manures. As only small traces are beneficial, larger amounts being poisonous, it is obvious that only small quantities would be needed, and, as the compounds are not usually very expensive, a considerable increase of crop for a relatively small outlay might be anticipated if no complicating factors intervened. Very much work will be required in the field to test the value of these substances, as their action may be influenced by the nature of the soil, climatic conditions, general conditions of manuring, and the crops grown. Some tests have already been made, especially in Japan, with boron and manganese, and these indicate a promising field for investigation. Above all, it is most important to realise that one is approaching an entirely unexplored field, and that it is inevitable that the results of the initial experiments will be contradictory, at least in appearance, so that it is necessary to keep an open mind on the subject, being ready to modify one’s ideas as circumstances require, as improved experimental methods lead on to more accurate results. BIBLIOGRAPHY _The references are to pages on which authors are mentioned. Papers to which no page-references are appended are not dealt with in the text._ PAGE ABBA, F. Ueber die Feinheit der biologischen Methode beim Nachweis des Arseniks. Centr. Bakt. Par. Abt. 2, IV, 806–8. (1898) 63 ADERHOLD, R. Zur Frage der Wirkung des Kupfers auf die Pflanze. Ber. Deut. bot. Gesell. XXIV, 112–8. (1906) --