The present paper contains the results of investigations on silver-leaf disease which are a continuation of those previously described by one of us (1,2) in earlier numbers of this periodical.

Some time ago it was thought desirable to duplicate as far as possible in different localities the experiments conducted on this disease. Hence most of the experiments described in this paper have been carried out both at Cambridge and at the John Innes Horticultural Institution, Merton.

An attempt has been made to determine the intensity of the biological processes in the soil during the most important periods of the Egyptian farm rotation. The fluctuations of the nitrate content in the surface soil have been taken as the most important index of this activity.

In all cases the moisture content of the soil limited these processes more than any other factor.

There was observed throughout the season in a cotton field a relatively large amount of nitrate, more than sufficient for the immediate needs of the cotton plant. The lack of response on the part of the Egyptian cotton crop to nitrogenous fertilisers may be accounted for in part, if not entirely, by the fact that nitrification in the soil is well ahead of the needs of the crop.

Nitrification under wheat and maize shows in general the same characteristics in Egypt as in other parts of the world; there is no accumulation of nitrate in the soil.

The winter fallow, depending for its water on the rainfall, may be a period of steady nitrification when the amount of the rainfall is sufficiently high.

1. The percentage of dry matter in the potato tuber is lowest in the skin and increases to the inner cortical layer, the zone containing the greater part of the vascular system, and decreases towards the centre of the tuber.

2. In each zone the proportion of dry matter is higher towards the umbilical than the terminal end of the tuber.

3. The percentage of nitrogen in the fresh material tends to decrease from the skin to the inner cortical layer and to increase in the medullary zone. Thus it increases from zone to zone in the opposite direction to the dry matter.

4. Nitrogen tends to increase with dry matter from the terminal to the umbilical end.

5. Microscopical examination shows the starch grains densest in the region of the vascular system, and decreasing towards the centre and surface of the tuber.

6. A high degree of correlation is found between the specific gravity and percentage dry matter of whole tubers.

7. For purposes of sampling the method of taking two radially opposed sectors, or two diagonally opposed eighths, was far more accurate than the coring method.

In a former paper, one of us has discussed the Palaeozoic soils of North Wales. In that paper, the Carboniferous soils were omitted as being rather apart from the other Palæozoic soils, which formed a convenient group for study by themselves. In the present paper, the authors discuss Carboniferous soils and the soils derived from the Northern Drift, together with the associated deposits of more recent origin.

1. The resistance of the hop-mildew (Sphaerotheca Humuli (DC.) Burr.) to polysulphide solutions varies according to its stage of development. The earliest stages after infection and antecedent to the production of conidiophores are the most resistant, requiring approximately a solution of double the concentration lethal for the “powdery” conidial stage. The “powdery” conidial stage occurring on young leaves is more resistant than the same stage on older leaves.

2. Conclusive proof has been obtained that with polysulphide solutions neither the total sulphur content nor the sulphide sulphur content gives an index of their fungicidal value.

3. The percentage of polysulphide sulphur in polysulphide solutions appears to be the factor determining their fungicidal value.

4. The fungicidal value of such solutions does not depend upon the nature of the polysulphides present.