FORCING-HOUSES. 181 



give air in the event of very hot and calm weather ; for I prefer giving 

 air by lifting up the lights to letting them slide down, because, when the 

 former method is adopted, no additional shade is thrown on the plants. 



The preceding plan is here particularly recommended for a vinery 

 only ; but I am confident that, by sinking the front wall below the level 

 of the ground and making a small change in the form of the bark-bed, 

 the same elevation of roof may be made equally applicable to the pine- stove, 

 and that no upright front glass ought, in any case whatever, to be used ; 

 for light can always be more beneficially admitted by adding to the length 

 of the roof, if that be properly elevated ; and much expence may be 

 saved both in the building and in fuel. For forcing the peach or nectarine 

 I must, however, observe that I think any house of the preceding dimen- 

 sions wholly improper ; and I propose to submit a plan for the improved 

 culture of those fruits to the Horticultural Society at a future opportunity. 



The vine often bleeds excessively when pruned in an improper season, 

 or when accidentally wounded, and I believe no mode of stopping the 

 flow of the sap is at present known to gardeners. I therefore mention 

 the following, which I discovered many years ago, and have always 

 practised with success : if to four parts of scraped cheese be added 

 one part of calcined oyster shells, or other pure calcareous earth, and 

 this composition be pressed strongly into the pores of the wood, the 

 sap will instantly cease to flow; so that the largest branch may of course 

 be taken off at any season with safety. 



XVIII. ON THE MANAGEMENT OF THE ONION. 

 [Read before the HORTICULTURAL SOCIETY, April 4th, 1809.] . 



THE first object of the Horticultural Society being to point out 

 improvements in the culture of those plants which are extensively useful 

 to the public, I send a few remarks on the management of one of these, the 

 onion : which both constitutes one of the humble luxuries of the poor, and 

 finds its way, in various forms, to the tables of the affluent and luxurious. 



Every bulbous-rooted plant, and indeed every plant which produces 

 leaves, and lives longer than one year, generates, in one season, the sap, 

 or vegetable blood, which composes the leaves and roots of the succeed- 

 ing spring ; and when the sap has accumulated during one or more 

 seasons, it is ultimately expended in the production of blossoms and 

 seeds. This reserved sap is deposited in, and composes in a great 



