414< Transactions ofilie London Horticultural Society. 



up weak, cause the flowers to be much smaller, and very much injure their 

 colours. By these means 1 have had them continue in good bloom for full 

 four weeks." 



21. On the Means of destroying the Red Sjnder in tlie Melon Frame. By 

 Thomas Andrew Knight, Esq., F.R.S., Pres. Read May 3. 1836. 



" The red spider is one of the most formidable enemies with which the 

 gardener has to contend, and against which he is least well prepared with the 

 means of defence. His peach and nectarine trees upon the open wall are 

 often considerably injured by it ; and the conservatory, the forcing-frame, and 

 the stove, scarcely present a plant which is not subject to sutler from its 

 attacks. When it appears upon trees growing upon walls in the open air, and 

 wherever water can be abundantly applied without material injury to the 

 plants, it is easily destroyed ; but there are, I believe, comparatively few 

 plants which are not much injured by having the lower surfaces of the leaves 

 much wetted. In a former communication I stated the destructive efi'ects 

 upon the melon plant of the application of water to the under surfaces of 

 the leaves, apparently owing to the cells of that surface of the leaf having 

 absorbed the lighter fluid, in the manner pointed out by M. Dutrochet, and 

 transmitted into the denser fluid the vital sap of the plant. 



" The aversion of the red spider to sulphur, or its inability to live in the 

 close vicinity of that substance, has long been known to gardeners ; and the 

 object of this communication is only to point out a more efficient mode of 

 employing it than has, I believe, hitherto been practised. The instrument 

 which I use bears a very close resemblance to those employed in fumigating 

 with tobacco, but it is filled with pieces of the wing feathers of pigeons or 

 poultry, amongst which a small quantity of flowers of sulphur is dispersed. 

 The receptacle is then closed with a lid, the front surface of which is perfo- 

 rated with many small holes, through which the air impelled by the bellows 

 passes, carrying with it a portion of flowers of sulphur. By shaking the 

 bellows, the feathers are made to change their position, bj' which many suc- 

 cessive portions of flowers of sulphur are made to escape, till the whole which 

 the receptacle contains is expended. 



" 1 first employed this instrument in the last summer in my melon-house, 

 in which, upon some of my plants, I observed a large number of red spiders. 

 After using it, I noticed with a lens in the web an immensity of minute parti- 

 cles of sulphur, in company with a very large number of red spiders ; but 

 upon examining my plants three days afterwards, I found the particles of 

 sulphur alone remained, and that the red spiders had either died or marched 

 off. I found no difficulty in causing many minute particles of sulphur to 

 adhere to the under surfaces of the leaves of all my plants, and during the 

 remainder of the summer I was not able to find a single red spider upon 

 them. 



" The form of the instrument for melon plants growing in hot-beds requires 

 to be considerably altered ; and the perforations for permitting the escape of 

 the flowers of sulphur should be lateral, instead of being in the front of the 

 lid : that should be made slightly conic, and of less width than the receptacle, 

 so as to come within it to a small depth ; by which means the whole of the 

 flowers of sulphur that escapes will be impelled forwards. The apertures 

 should be confined to one side of the lid, which should not sink wholly into 

 the receptacle ; and through such apertures the flowers of sulphur will be 

 made to escape below the level of the leaves of the melon in the common 

 frame, and be dispersed over the under surfaces of its leaves. 



" I applied flowers of sulphur in several other cases in the last summer, 

 and always with success ; and I am applying it to my peach-house and vinery, 

 instead of water from an engine, and I have reason to believe with perfect 

 success. 



" My friend Mr. Williams of Pitmaston has perfectly succeeded in banishing 

 the red spider from his melon-house, by causing sulphur to evaporate from 



