" Rose Grower" says : " I note in the Gardeners' Monthly remedies for the cure of mildew. Is anything known of its cause and prevention?"

[Under the name of mildew we are speaking of small funguses. These, like the whole mushroom family, only grow when there are combined moisture and a degree of heat just suited to them. They seem to require exact conditions for growth to a fine point not required by a higher order of vegetation. We may for instance expose a piece of bread to the weather. If it get wet and the temperature is but a few degrees above freezing point, no fungus at once appears. If the temperature be above 500, no fungus appears; at least not the cob-webby form which is so destructive to vegetation. But if the temperature be about the dew point, the bread will be found as soon as the dew is off completely covered with a fine silky organism. It was the exact temperature in connection with the moisture that induced the rapid fungous growth. Now in rose culture few are troubled by mildew when a temperature of 550 is steadily maintained in connection with the humidity of the atmosphere. If a draft of cool air be admitted so as to suddenly alter the hygrometric conditions, or the temperature in connection therewith, mildew may follow.

Sulphur applications may kill it after it has started.

But the conditions of the plant may favor the growth. There is no doubt now but mildews will attack perfectly healthy vegetation, but it is also true that they prefer that which is either dead or with low vital power to that which is strong and vigorous. The weakest leaves are the first attacked. It is therefore wise in the rose grower to study those laws of health related to roses or other plants. A large number of rose growers have plants that by bad treatment are under low vital conditions, and these are unquestionably more liable to mildew than perfectly healthy plants. The average rose grower knows very little about the laws of health as applied to the plants he grows. - Ed. G. M].