148 



KNOWLEDGE. 



[July 1, 1898. 



independent of maternal care, are laid in the so-called 

 " ephippium " — a case developed in the mother for this 

 special purpose, and subsequently detached. An old 

 writer has been scoffed at for speaking of Daphniu judex 

 as a " wonderful insect." It is not in modern classifica- 

 tion an insect. Of forms now known which belong to the 

 same social set it is by no means the most eccentric. It 

 is not rare, but, on the contrary, multitudinously common. 

 None the less, it is to my mind easy to sympathize with 

 Bradley when he caUed it wonderful. 



A CLASSIC LEGACY OF AGRICULTURE.-U. 



By .John Mills. 



THERE is no more beneiicial creation of wealth than 

 that which arises from the complete development 

 of the resources of the soil and the correct 

 manipulation of its products. Better education 

 in agriculture would contribute largely to an 

 intelligent appreciation of the problems which arise in 

 farming as a business, and increase the efficiency of the 

 mental machinery destined to direct operations in the field. 

 Farmers of the future, whose minds are thus counterpoised 

 and adjusted so as to retain their equilibrium under all 

 conditions — favourable and unfavourable — will play an 

 important part in the struggle for supremacy between 

 civilized countries ; and, so equipped, complete confidence 

 may be placed in the ability of the tillers of the soil in 

 our own country to maintain a secure place in the markets 

 with rivals, distant and near, who make it their chief 

 occupation to supply cur population with food. In the 

 attainment of such knowledge a great multitude of facts 

 present themselves for consideration, each of which requires 

 due thought to discern its bearing on the whole and to 

 assign it a place in agriculture so as to render the science 

 of maximum usefulness. Thus, the quantity and quality 

 of the crops, the character of the soil and of the climate, 

 differences in the habits of plants, general economy of the 

 farm, and so on, give rise to a number of questions which 

 form a sort of algebraic equation involving many unknown 

 quantities, and to solve which requires not only a vast 

 amount of exact observation, but also profound skill in 

 the marshalling of facts and manipulation of data. The 

 experiments at Eothamsted, conducted by Sir John Lawes 

 and Sir Henry Gilbert, are of this complicated description, 

 some of the results being merely tentative. 



The object to be attained in the cultivation of root crops 

 is to encourage, by artificial means, a quite abnormal 

 development of a particular part of the plant. If, for 

 example, the turnip plant were grown for its natural seed- 

 product oil, a heavier soil would be more suitable than 

 when the object is to develop the swollen root. When 

 grown in ordinary soil without manure, either for a few 

 years in succession or even in rotation, root crops scon 

 revert to the uncultivated condition ; they depend for 

 luxuriant growth on an abundance of nitrogenous as well as 

 mineral constituents within the soil, and they are therefore 

 generally highly manured. In the accompanying table, 

 the results obtained with Norfolk white turnips are shown, 

 NoBFOLK White Tuenips, without Manube, axd with 

 Faemtaed Manuek. 



and it will be noted that when grown without manure the 

 crop dwindles down almost to zero, whilst with farmyard 

 manure there is a marked increase year by year. The 

 form of the unmanured root resembles that of a carrot 

 more than a turnip, and its composition is totally different 

 from the cultivated root. There is, indeed, much more 

 nitrogen taken up by the latter, but the percentage of that 

 element — apparently lower than in the unmanured plant — 

 is masked by the accumulation of a large amount of other 

 matters which render the plant an important food crop. 

 The average proportion of leaf to root under different 

 conditions as to manuring clearly indicates the suscepti- 

 bility of these plants to artificial influences : to one thousand 

 of root with mineral manure alone, the yield of leaf 

 being three hundred and twenty-nine ; with mineral and 

 ammonium salts, four hundred and thirty-four ; and with 

 mineral and ammonium salts and rape cake, six hundred. 



Potatoes have been grown on the estate for twenty-two 

 years in succession, different sorts being selected on the 

 supposition that in growing the crop year after year change 

 was desirable, especially with a view to the avoidance or 

 lessening of disease. It is now an established fact that 

 season has much to do with the development of the potato 

 disease, and these experiments show that there was on the 

 average much more disease in the wetter seasons. When 

 the unsuitable weather comes, those tubers suffer the most 

 which have the richest juice — that is, the least fixity of 

 composition. The first material change in the develop- 

 ment of the disease is, apparently, the destruction of 

 starch and the formation of sugar ; there is also a con- 

 siderable loss of organic and chiefly ?io?! -nitrogenous sub- 

 stance, due in part to the decomposition of the produced 

 sugar, but probably in some measure to the evolution of 

 carbonic acid, as a coincident of the growth of the fungus 

 at the expense of ready-formed organic substance, this being 

 a characteristic of the growth of such non-chlorophyllous 

 plants. Regarding the cultivation of the plant under varying 

 conditions, it is somewhat interesting to observe that the 

 produce of starch per acre was about one thousand one 

 hundred pounds without manure, nearly two thousand 

 pounds with purely mineral manure, and with nitrogenous 

 and mineral manures together about three thousand four 

 hundred pounds. In other words, the increased produce 

 of starch by the use of the mineral and nitrogenous 

 manures together was more than one ton per acre. That 

 is to say, there was a great increase in the production of the 

 «o?}-nitrogenous constituent, starch, by the use of nitrogen 

 in manure — a striking result, indeed, and one more hint 

 Ihat nature will have her own way, paradoxical though it 

 may seem to us. In truth, it is for the production of the 

 non-nitrogenous substances — starch, sugar, and cellulose — 

 that our direct nitrogenous manures are chiefly used 1 



The fixation of free nitrogen directly from the atmo- 

 sphere is a subject which has engaged the attention of 

 many inquirers, notably Sir John Lawes and Sir Henry 

 Gilbert at Eothamsted ; and a theme of much controversy 

 among scientific men for many years past has been — 

 " How is the fixation of nitrogen to be explained?" 

 Diversity of opinion still obtains on this question, and, 

 unfortunately, there is yet much to learn before a satis- 

 factory answer can be given ; but though the explanation 

 is wanting there can be no doubt that the fact of the 

 fixation of free nitrogen in the growth of leguminosffi — 

 clover, vetches, peas, beans, sainfoin, lucerne, and so on — 

 under the influence of suitable microbe infection of the 

 soil, and of the resulting nodule formation on the roots, 

 may be considered as fully established. What, then, is 

 the basis of this conclusion ? Recent experiments at 

 Eothamsted show that, by adding to a sterilized sandy 



