It is unlikely that as a formulated problem any consideration of settled crop-husbandry is of greater antiquity than the cereal yield problem. In its broad form it embraces all the possible means of increasing the output of grain per unit area. The earliest civilizations of Mesopotamia and Egypt must have been compelled to explore these means as soon as they began to encounter the limitations to cultivable area which dwelling in fixed communities imposed. Wheat and barley were their principal food stuffs so that the cereal yield problem, the most comprehensive concern of present-day agriculture, goes back to the remotest antiquity. It must have evoked incessant effort along divers lines and the cumulative result is appreciable from a comparison of the best cereal races of to-day and the forms which like Hordeum spontaneum and Triticum dicoccum dicoccoides have been regarded as the progenitor types. Unfortunately it is not possible to trace back very far the sequence of the solution of the problem as constituted by improvements in husbandry and the utilization of better cereal forms. Fragments of information may be culled from the writings of various periods but they are of doubtful value. The author's reliability is often in question, the unit of measure uncertain, and even the identity of the crop a matter of doubt. Herodotus' well-known story, passed on from another, of increases of 200 and even 300 fold yielded by barley in Mesopotamia in 500 B.c. is possibly the oldest fragment. It is difficult to interpret but it gains colour from the further statement that the leaves of the plant were of the width of four fingers. Concerning progress in England, while reasonably precise information goes back no further than forty years, there are widely separated records of sufficient worth to indicate the historical trend. It has been deduced from the Manorial Records that at the time when that system had become established there was a flat rate of about ten bushels per acre for wheat. Much later, when Sir Charles Davenant compiled An Essay upon the Probable Methods of making a People Gainers in the Ballance of Trade (published 1699), he computed the “neat produce” of eight million acres of arable land to be 79 million bushels of grain.

No abstract

Considerations which are dealt with at length in Appendix III governed the form of the investigation upon tillering. In essence, the intention was to compare the pure lines P and A and to explore the possibilities of making accurate determinations of tillering. For reasons discussed in the Appendix, special steps were taken to secure for observation a population of plants which had had as great a uniformity of conditions as was attainable. The selection and sowing of the seed have been described in § I above. To promote further uniformity, plants of the following categories were excluded from observation: (i) all the plants of end rows; (ii) the end plants of all rows; (iii) plants which did not germinate on 26. iii. or 27. iii. (these days constituted the “modal” 2-day period of germination for the whole population); (iv) plants damaged to a noticeable degree by wire-worm or any other such agency; (v) plants whose immediate neighbour(s) in the row had died.

SUMMARY This paper reports the results of experiments carried out in Surrey and Cardiganshire (lat. 51o 19′ N. and 52o 25′ N.) and a t Werribee in Victoria (lat. 37o 54′ S.) designed to test some Australian and British wheats grown under various periods of illumination. Light of weak intensity (4–5 c.P.) was employed to prolong the daily period.2. Generally the Australian varieties were “earlier” at all centers under all periods of light than the British. A sharp distinction between the reaction of spring and winter varieties was observed under short periods of light. Retardation or omission of floral development was always accompanied by prolonged vegetative vigour. The influence of such treatments upon the longevity of the plants was observed. Observations are made upon the relationship of the photoperiodic response to the geographic source of varieties. The results are very briefly considered from the standpoint of the C/N hypothesis and the utilisation of the products of photosynthesis. Certain economic aspects of the work are indicated.