charges per ton. Attempts were in 1921 being made to replace basic
slag Dy finely ground mineral phosphates as a fertilizer for grass
land. American experience has always been favourable to these
ground phosphates, and recent experiments in England have
demonstrated that they effect in poor pastures the same encourage-
ment of clover as is obtained from basic slag, even upon such un-
promising land as the clays in the dry Essex climate. The phosphate
rock from Nauru Island, that has passed from German hands into
the control of the British Government, may prove of special value
for application in this finely ground but otherwise untreated con-
dition.
Plant Breeding. Probably the plant breeders have during 1900-20 rendered the greatest services to agriculture, inasmuch as improvements in this direction the introduction of new varieties giving large yields, better quality and more resistant to disease are at once appreciated by the farmer and require no alterations in the methods of cultivation. It has been found possible to apply Mendelian principles with comparative sim- plicity and accuracy to the breeding of new varieties of plants, especially of cereals, and the results achieved have already experienced considerable commercial development in the case of wheat, barley, oats, maize, sugar-cane and cotton. The value of the Mendelian principle lies in the power it gives of combining in one of the selected descendants of a cross-bred individual un- related valuable characters possessed by the parents separately.
In the case of wheat Biffen has shown that among the Mendelian characters that are transmitted as unchanged units are such quanti- tative properties as the resistance to disease, the normal percentage of nitrogen in the grain and the " strength " of the flour resulting from it, the stiffness of the straw, etc. One of the chief desiderata as regards English wheat has been an improvement in its strength, i.e. the capacity to yield a spongy elastic dough which will .bake into a light loaf of large volume. This strength factor which is connected with the amount of gluten and therefore with the percentage of nitrogen in the flour is as a rule the property of spring wheats grown in a " steppe climate " with a short period of growth, with consider- able rainfall in the early months exchanged for great heat and al- most complete dryness before harvest. Wheats from Hungary, South Russia, Manitoba and the great plains of North America possess this quality, and Leclerc ana Leavett have shown by sowing the same seed in different states how potent is the effect of environ- ment and climate in determining the percentage of nitrogen and the strength of wheat. As a rule any of the strong wheats brought either from continental or American sources lose their strength completely when grown under English conditions. One wheat, however, of Galician origin but widely grown in America under the name of Red Fife, so widely indeed as to be the dominant constituent of such commercial grades as Manitoba and No. I Northern, does to a large measure retain its strength in England, the strength in this case being congenital and not the product of environment. Red Fife is, however, a poor cropper on most English soil, yielding but 3 qr. per ac. where the typical English wheats will yield four or five. Biffen has, however, employed it as a parent in the hope of combin- ing the strength of the one parent with the cropping power of the other and one of the results of this cross, a wheat called Yeoman, issued to the public in 1915, is on its congenital soils the warmer and better soils of the east and south-east of England probably the heaviest cropper grown. Further, the quality of the grain is so high that the miller can use it without any mixture of strong foreign wheats, such as are necessary to the extent of 40% or more with ordinary English wheat. Another of Biffen's wheats, Little Joss, by its power of resisting rust, has proved a very heavy cropper and is now extensively grown on soils that remain fairly dry and warm throughout the winter. Saunders in Canada has effected a very con- siderable extension of the wheat area by the introduction of a wheat called " Marquis," another hybrid with Red Fife as one parent, which combines the good quality of Red Fife with a shorter period of growth and an earlier ripening habit, thus rendering wheat- growing safe in wide areas, as in parts of Alberta, where the crop was liable to ruin through the onset of early autumn frosts before harvest had been completed. On the average Marquis ripens six days earlier than Red Fife and thus in the Central Prairie region where firsts are expected between Aug. 27 and Sept. 2 Marquis can generally be grown safely though Red Fife is liable to be caught. In part the extension of Marquis may be put down to its superior cropping powers, but for one reason or another it has largely dis- placed all other spring wheats in the North-West. In 1918 the area under Marquis in Minnesota, the Dakotas, Montana, Manitoba, Saskatchewan and Alberta was estimated to amount to 20,000,000 ac. and the crop in Canada alone to 129,000,000 bus. all the produce of what was but a single plant in 1903!
Immunity from Disease. The inheritance of immunity from disease is best illustrated by the discovery of potatoes immune to wart disease.
About 1897 attention was drawn to the prevalence in certain
parts of England and Wales of a disease of potatoes, generally found in old cottage gardens and allotments, which causes the potatoes to degenerate into a mass of dark corky excrescences and will in bad cases destroy the crop entirely. The disease is due to the attack of a lowly organised fungus, and the difficulty of dealing with it is due to the fact that once established in the soil the spores or some resting form of the fungus retain their life for an indefinite period of many years. Once the soil has become infected no practicable means has been found of cleaning it; even leaving the land down to grass for ten years has been found ineffective. Considerable areas in the industrial districts of Lancashire, Cheshire, Stafford and Shrop- shire, North and South Wales are subject to the disease and it became more widely distributed throughout the West of England as a result af the great shortage of seed potatoes in 1917, which caused men to plant anything that was available without inquiring into its origin.
The consequences would undoubtedly have been the complete destruction of potato-growing in those districts had it not been observed that one or two types of potatoes could be found growing unharmed in some of the old infected gardens. Further examination proved that these varieties were really immune to the disease, how- ever heavily infected the soil, and though in themselves they pos- sessed little commercial value they were at once employed as seed parents and have become the source of a new race of potatoes immune to wart diseases. Many of these are now proving to be good market varieties of heavy cropping power and by their aid potato- growing has been rendered possible in the infected areas which other- wise inevitably would have spread until the whole country would have been involved. As the disease has also obtained a foothold (its original habitat is unknown) in North America, Holland, Bel- gium and Germany, the value of this discovery of immunity is difficult to overestimate. From the study of this and other cases the conviction gains ground that the most fruitful method of dealing with plant disease will always be by the search for immunity rather than by methods of treatment.
Selection. In the improvement of cereals considerable advantages have been derived by working on another principle than that of breeding, i.e. pure line selection. Very little im- provement in a variety can be effected by what may be called " mass selection." If in going over a field of wheat a collection is made of the longest ears, or again if the heaviest grains are sorted out, no perceptible improvement is visible in the crop grown from the selection, not even if the process is repeated generation after generation. The superiority of the individuals selected has been due to some accident of nutrition and is not transmissible to the offspring. If, however, the selected individuals are sown separately, here and there among them will be found one which in the next and succeeding generations still preserves some superiority which is congenital to it and is maintained in succeed- ing generations even when the seed is worked up to a large crop.
An ordinary variety, say of wheat, really consists of an indefinite mixture of sub-varieties each of which, for many generations at least, breeds true in the case of cereals which are self-fertilized. Thus " pure lines " may be selected from single seeds of such self- fertilized plants and worked up to commercial stocks of seed. These pure lines may have some superiority, never, however, great, in cropping power over the mixed variety from which they are derived, and are also appreciably more uniform in such details as time of ripening and length of straw.
It has become evident that every commercial variety of cereals, even if of deliberately cross-bred origin, will be improved by pure line selections from time to time.
Nutrition. It was still difficult in 1921 to discuss in any detail the progress that is being made in the study of animal nutrition, in regard to which the teachings of the scientific man have had much less effect upon the practice of the farmer than has been the case when the nutrition of the plant has been concerned.
The great shortage of cattle food during the war, notably in 1917 and 1918 when no tonnage could be spared for cattle food, did reveal two things, first, the dependence upon imported corn and oil seeds that British meat and milk production had fallen into, and secondly, the enormous waste that had been going on. It was estimated that the normal output of meat, milk and other animal products did not represent one-half, possibly not more than a third, of the amount that could have been obtained, not merely theoretically, but even in properly informed practice. At the same time certain lacunae in our theory were disclosed, which prevent the scientific man from setting out with any accuracy the limits within which the fattening of animals will proceed most economically. It will be seen that the problem is a very complex one. On the one hand, as regards the amount of food fed over and above the maintenance ration, the law of diminishing returns is found to hold for the amount of daily increase; on the other hand, the slower the rate of fattening, the
