230 Commercial Gardening 



greenhouse putty called "Plastine". This is double the cost of ordinary 

 putty, but it never gets hard, and repairs can be carried out with the 

 greatest ease; there is also less shrinkage with this, and consequently 

 less leakage. All ironwork should be coated with iron-oxide paint. 



Glass can be got in all sizes, and a very usual size is 20 in. by 16 in., 

 and 24 in. by 18 in., the panes being put in lengthways; more bars are 

 required this way, but the house is stronger. The glass used should 

 always be 21-oz. [w. M. B.] 



Greenhouses on Rails. About twenty years ago the idea of having 

 movable greenhouses occurred to the Horticultural Travelling Structures 

 Company, and many of their buildings are now to be seen in actual use by 

 market growers in all parts of the kingdom. This company has protected 

 and patented its structures, and are the only builders in the United 

 Kingdom. Quite recently some American growers have had similar green- 

 houses built on the same principles. The system consists in having a rail 

 at each side upon which the greenhouse rests and runs along by means 

 of wheels when it is necessary to move it from one crop over another. 

 The Plate shows how the rails are fixed at the sides and between two 

 houses. The rail in the centre is of rolled steel channel iron, and rests 

 on iron stanchions bedded in concrete, and serves the purpose of a guttei- 

 as well as a railway. The outside rails either rest on brickwork or on 

 stanchions; in the latter case the spaces between the stanchions being 

 filled in with creosoted boarding. 



These travelling glasshouses are used chiefly for bulbs, Strawberries, 

 and low-growing crops generally, and in cases where a rotation is required 

 without the application of much heat for forcing purposes. In England 

 where the houses are in use, three crops of bulbs chiefly Narcissi and 

 one crop of Tomatoes, are generally produced during the year. In the 

 Channel Islands, however, four crops of bulbs are often grown one after 

 the other. 



A modified type of glasshouse has recently been brought out by the 

 same company. It is from 40 to 50 ft. wide, with high sides to the eaves 

 to allow greater headroom for the crops. Such wide houses are common 

 in the United States, where the roofs are trussed by rolled rods fitted 

 together by forgings or screwed together in castings. This wide type of 

 house is considered superior to the older forms although it is more ex- 

 pensive to erect. The Horticultural Travelling Structures Company have 

 substituted substantial wires for the rods used in the American houses, 

 and this reduces the cost considerably, and the new system, which has been 

 patented, can be applied to houses 30 ft. wide as well as to those of wider 

 dimensions. 



The other photographs show some of the more generally adopted glass- 

 houses used by market nurserymen in England. They are from designs 

 made by Messrs. W. Duncan Tucker & Sons, of Tottenham, who not only 

 erect them for the trade, but also supply timber already prepared to 

 growers who prefer to erect their own greenhouses. 



