I885.J 



AND HORTICULTURIST. 



'97 



Greenhouse and House Gardening. 



COMMUNICATIONS. 



NOTES ON MILDEW AND OTHER TOPICS. 

 BY JOHN MURCHIE. 



Much interest seems to be taken in the subject 

 of "Mildew on Roses" and its cause. I am ot 

 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 ad- 

 mitted 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 90", the air is chilly 

 outside, and the sun is shining brightly. Then, 

 nine times out of ten, up go four or five venti- 

 lators, 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 evapor- 

 ation 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. At out the 

 middle of March I had in flower plants of Cattleya 

 Skinneri and C. Triana. The plant of C. Skin- 

 neri had eighteen flowers. I removed the pollen 

 balls from three of the flowers for the purpose of 

 hybridizing Trians 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 pro- 

 duced two flowers on one stem for three years in 

 succession. I asked Mr. O'Brien to mark and re- 

 move 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 Phaljenopsis 

 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 inter- 

 esting. Sharon, Pa.., April nth, 1S85. 



[There is no doubt but plants with low vital 

 power become afflicted with mildew, and other 

 fungus diseases, when plants under the best con- 

 ditions of life will escape. It may be necessary to 

 explain that a plant under these low vital con- 

 ditions 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 



