In addition to the Director, Mr. R. G. Hatton, the graded staff at the Station consists of two senior Assistants and one Assistant. A physiologist from the Imperial College of Science is also working in collaboration continuously at East Malling. Three special assistants are working in the Mycological and Entomological Laboratories, and nine special assistants in the Pomological Section. Two post graduate voluntary workers have also been assisting. An Exhibitions Officer and Guide Demonstrator has been fully occupied throughout the year.

The sums included for East Malling in the general grant from the Development Fund to the Ministry were :

Experimental and Research Station, Cheshunt, Herts.

The purpose of this Station is to carry out investigations upon the many problems which arise in the cultivation of crops under glass. The equipment includes 16 glasshouses, in which manurial and other cultural trials are conducted on tomatoes and cucumbers annually, the work including the influence of manures on yield and disease resistance; soil sterilisation experiments and variety trials are also made.

Other groups of studies are directed towards the control of the diseases and pests of glasshouse plants; the effect of manurial treatment upon the composition of the tomato plant; the lime factor in relation to glasshouse soils; the decomposition of turf; green manuring under glass; the fertilising effect which carbon dioxide supplied in various quantities to the air of the glasshouse may exercise upon plants; the breeding of new varieties resistant to disease. In addition, a considerable amount of advisory work is undertaken, by correspondence, personal interviews and visits to nurseries.

It is now possible to summarise the results of cucumber experiments conducted during the years 1924-27 as follows:

(1) When the cucumber is grown in a bed of loam and stable manure for one complete season, the bed is rendered unsuitable for cucumber cultivation during the following

season.

(2) The continuous cultivation of the cucumber in beds. placed over the same soil for a number of years contaminates the base. The actual process of contamination is not understood, but it seems reasonable to suppose that the contamination is washed down from the beds and accumulates in the base.

(3) When the roots of cucumber plants come in contact with the contaminated base their health and fruiting powers are seriously impaired.

(4) Sterilisation of a contaminated base by means of steain causes a marked improvement in crop and presumably removes the base contamination.

(5) The beneficial effects of steaming last for one year only, and therefore in old soil it is necessary to steam every

year.

(6) The degree of improvement in the crop which results from steaming the base is affected by the nature of the weather during the early stages of growth.

When the weather is favourable, the plant's increased vitality enables it to make full use of the sterilised soil. During unfavourable weather, the plants do not make such a good start and in some cases sterilisation of the base has caused a slight retardation of growth in the early stages.

(7) It seems advisable to delay steaming the base as long as possible, so as to take advantage of planting in warmed soil.

(8) By spreading and steaming the beds at the end of the season, a higher crop has been obtained under the Experimental Station conditions than by removing the old beds and substituting new compost.

(9) The replacement of a contaminated base by new soil of a poor gravel nature caused an immediate improvement in crop this year, and the plants retained their vigour to the end of the season.

(10) A crop of practically two flats per foot has been obtained over a concrete covered base, when the bed was sufficiently big, namely, the previous year's bed spread and steamed.

(11) The admixture of washed ashes in the beds this year was an advantage.

(12) Finally, the cucumber plant requires a well-aerated bed and a well-drained base, if it is to yield the best crop. During the same period investigation of the causes underlying "blotchy ripening of the tomato have revealed the following:

(1) Blotchy ripening of tomato fruits is the result of malnutrition in respect of potash and nitrogen, especially the former. Phosphates seem to be unimportant in this respect.

(2) The proportion of blotchy fruits may be reduced to less than 1 per cent. by suitable applications of sulphate of potash and sulphate of ammonia.

(3) Blotchy ripening has not been eliminated entirely by manurial treatment. Other factors, probably climatic in nature, play some part in the incidence of this disorder.

(4) Root-invading fungi, such as Colletotrichum atramentarium, interfere with the feeding of the plant and indirectly cause blotchiness of the fruit.

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(5) Exposure of the fruits to excessive sunlight causes a type of blotchiness known as green back" if the nitrogen and potash supply is inadequate.

(6) Blotchy ripening may be accompanied by necrosis of the vascular bundles of the fruit.

Experiments in the fertilising effect of carbon dioxide on glasshouse plants have been continued. The earlier conclusion that daily treatment for 1 to 13 hours, with atmospheres containing not more than 1 per cent. carbon dioxide, is beneficial to tomatoes has been amply confirmed. An apparatus for the continuous supply of carbon dioxide has been useless, but a stove burning patent fuel, which burns almost completely to carbon dioxide, has given promising results, in a small chamber in which 56 tomato plants were grown. Where this stove was used during two hours in the morning, and a similar period in the afternoon, the crop was increased from 16 per cent. to 30 per cent.

The Red Spider Mite, Tetranychus telarius L., which is a serious menace to the tomato and cucumber crops, has been studied during the past three years, and considerable advances towards complete control have been made by improved methods of house disinfection and fumigation of the pest with naphthalene. Further improvements are being explored.

In addition to the Director, Mr. W. F. Bewley, D.Sc., the authorised graded staff of the station for 1926-27 was two senior assistants and one junior assistant.

The sums included for Cheshunt in the general grants from the Development Fund to the Ministry were :

Horticultural Research Station, Cambridge University.

The young trees planted in 1924 in the first portion of the orchard have done well, and those in the second portion planted in the autumn of 1925 appear to be thoroughly established.

A number of hybrid apples and plums fruited for the first time. this season. Some of the apples are worth testing further, but none of the plums were considered to be worth a further trial.

A second year's trial of American strawberries brought out the differences between the various sorts more clearly than in the preceding year. None of the varieties showed the all-round excellence of the best English sorts, but one at least produced

an exceptionally heavy crop, and several others were characterized by richly coloured flesh. A preliminary trial of the fruit for bottling and jam-making was made by Messrs. Chivers of Histon. The information obtained from the field and factory should be of value in the hybridizing experiments for which provision is now being made.

The F2 onion cultures were of interest both genetically and from the commercial point of view. They indicate the possibility of raising forms less liable to rot in store, that is, forms. with some measure of resistance to the attacks of Botrytis, and also forms resistant to the common onion mildew. They provided material also for the investigation of the inheritance of colour, shape, size and growth period. Selfed" seed from suitable plants will be saved for the further study of these characters in the F, generation.

3

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Seed from the mass selection cultures from the first comparative trials of commercial stocks was tested under market garden conditions in Bedfordshire with satisfactory results: nucleus stocks of purer seed are now being worked up for similar trials.

Vegetative propagation by means of bulblets has proved useful during the investigations. It may have commercial possibilities also, for the bulblets set out in March have produced exceptionally large bulbs under ordinary garden conditions. A strain which produces bulblets spontaneously has now been isolated.

On the assumption that the mixture of types in crops of Brussels sprouts is due to out-crossing, an investigation into the subject has been started. The results obtained so far indicate that most plants are either sterile or only slightly fertile with their own pollen, but one plant in the series under test has set seed so freely under conditions where out-pollination was impossible that it would appear that self-fertile individuals can be found. If such a strain can be isolated the raising of pure stocks will be greatly simplified. A supply of seed from a number of selected plants which were allowed to inter-pollinate has been harvested for certain field trials.

The parsnip roots selected in 1925 seeded freely, partly under controlled and partly under natural conditions. The plants proved to be self-fertile, but the time interval between the shedding of the pollen and the maturation of the stigma was so great that bagged inflorescences set little, if any, seed, and artificial pollination was found necessary.

The investigations on the effects of climate on a series of vegetable crops and on the physics of spray-fluids was continued on the lines described in previous reports. A large mass of data on the former subject is now being statistically examined with a view to publication.

In addition to the Director, Professor Sir R. H. Biffen, M.A., F.R.S., the authorised graded staff of the Station for 1926-27 was two senior assistants (one of whom is Deputy Director) and one junior assistant.

The following sums were included for the Station in the general grants made from the Development Fund to the Ministry :

Academic year, 1st October to 30th September.

1925-26. 1926-27.

£

£

Salaries, including superannuation ... 1,430
Maintenance, including wages

1,342

420

558

Silver-leaf Investigation Station, Cambridge School of Botany.

The object of this Research Station is to carry out investigations upon the serious Silver-leaf disease of fruit trees, with the view to obtaining effective means of control. An experimental plantation of plums and a greenhouse for pot plants on the farm of the University School of Agriculture have been provided to facilitate these researches.

The following are the salient features of the work of the year :Many of the results obtained are confirmatory of those published in the paper "Silver-leaf Disease, V" referred to in the last report.

It has again been found practically impossible to infect fresh exposures in plum trees with spores of Stereum purpureum during the months of June, July and August, whereas infection is readily induced during the other months of the year.

With regard to the protection of wounds against the fungus, excellent results have again been obtained with soft grafting wax and home-made whitelead paint. Less satisfactory results, however, have been obtained this year with home-made red oxide paint. New substances that have been tried as wound protectives have not proved satisfactory.

Experiments have been carried out to try to determine the rate of gum-formation at different times of the year in fresh exposures of plum twigs not deliberately inoculated with the spores of the fungus. It has been found that the rate of gumformation is very slow in the winter months, but increases during spring and reaches a maximum in June and July, often culminating in the latter months in the formation of a "gum-barrier."

It having been reported from Holland that certain varieties of pear trees, upon inoculation with S. purpureum, readily become affected there with Silver-leaf disease, inoculation experiments have been carried out with these varieties, but with negative results. It is difficult to account for this divergence, but in previous years it has been impossible to induce Silver-leaf in pears in this country by inoculation.