Much interest seems to be taken in the subject of "Mildew on Roses" and its cause. I am of your opinion, Mr. Editor, that mildew very seldom attacks healthy plants, and when it does we are simply told "it is a chill." Roses are much more liable to the attacks of mildew in autumn and spring than in winter, when little or no air is admitted to the house. Now I will state what I consider the most prolific source - cause - of mildew; namely, the manner in which the plants receive this chill or check, which, if properly understood, mildew would seldom be seen, at least on healthy roses.

Through carelessness and neglect the house is allowed to rise to too high a temperature, the house is found standing at 900, the air is chilly outside, and the sun is shining brightly. Then, nine times out of ten, up go four or five ventilators, and out rushes the heated air carrying with it every particle of moisture the house contained, causing the tender points of the shoots and young leaves to droop or wilt by the sudden evaporation of their sap. The higher the temperature of the house the more moisture the atmosphere contains. The freeing of this heated air is followed by a drier air, which absorbs moisture quickly, hence the evaporation, and hence the chill, for I think this evaporation causes the temperature of the young shoots and leaves to be much lower than is indicated by the thermometer in the house.

I have not scientific lore enough to explain this as fully as I would wish, but I am satisfied of the effect produced by this cause. How evaporation affects the organism of the tender wood and leaves, causing them to wilt, I do not know (perhaps the Editor will explain). This much we do know; they do wilt, and I believe from this cause.

One such chill has a worse effect on healthy roses than would be caused by the temperature of the house touching freezing point if the change was gradual. The plants receive a chill in this way, when to all appearances there has been no such thing as a draught of cold air. When the house is thus overheated, the paths and benches should be thoroughly sprinkled and air admitted sparingly.

I was interested in the duration of the flowers of Cyclamen, as recorded by Mr. George C. Butz, and will give an instance where the removal of pollen shortened the life of the flower. About the middle of March I had in flower plants of Cattleya Skinneri and C. Trianae. The plant of C. Skin-neri had eighteen flowers. I removed the pollen balls from three of the flowers for the purpose of hybridizing Trianae on the morning following. The lips of the three flowers were rolled tightly around the column, and they faded and fell off more than ten days before the other fifteen flowers. The flower of C. Trianae, to which the pollen was applied, began to droop almost at once, and promises to give a crop of seed; but the getting a crop of plants is not so easy. A plant of Cypri-pedium insigne here with Mr. O'Brien has produced two flowers on one stem for three years in succession. I asked Mr. O'Brien to mark and remove it, and try to perpetuate it, but he neglected to do so. We will watch it another year.

I send you with this a flower of Phalasnopsis Schilleriana, with three very perfect lips. There are two flowers exactly similar on the same spike.

Could you not induce the Rev. L. J. Templin to continue his description of Interesting Vegetable Forms ? It is very instructive as well as interesting. Sharon, Pa., April nth, 1885.

[There is no doubt but plants with low vital power become afflicted with mildew, and other fungus diseases, when plants under the best conditions of life will escape. It may be necessary to explain that a plant under these low vital conditions need not necessarily be diseased in the full sense of the word, for, it is probably here that so much confusion exists between two great classes of intelligent people - one, those who believe the minute vegetable organisms attack only plants already diseased, and those who are satisfied they will attack the most healthy plants. For instance, in the north of Europe the English gooseberry is at home. It delights in a moist climate. When it is planted in more Southern latitudes where the climate is drier, it mildews. The plants are still healthy - at least no one would call them diseased but the drier climate somewhat weakens their power of resistance, and then they are to mildew an easy prey. So with the garden pea, also a lover of a cool northern climate. Those we sow early bloom and keep healthy to the last, but late sown peas mildew, and come to nothing. They are healthy, but yet weak.

It is a nice distinction between a low vital power, and actual unhealth-fulness, but yet an important one.

Mr. Murchie's suggestion about the evaporation from young growth may also be seen by these illustrations, to have good ground; for no doubt it is the strain on the juices of peas and gooseberries - plants accustomed to a moister climate - that first leads them to tire of the great struggle for life. - Ed. G. M].