go 



Annals of Horticulture. 



Greenhouses. Many departures are making in the con- 

 struction of glass houses for florists' use. One of the most 

 important innovations is the tendency to use the common 

 wrought-iron steam or gas-pipes for heating purposes, in 

 preference to the old cast-iron pipes, both for hot water un- 

 der pressure and steam-heating \ and this has introduced a 

 system of overhead piping which has overturned some of 

 houses", the common notions of greenhouse-heating. Steam is also 

 contending for supremacy over hot-water, but neither agent 

 can be said to have made signal victories for general purposes. 

 It will undoubtedly be found that both agents possess supe- 

 rior advantages for particular purposes. The fact that steam 

 has often dislodged hot water systems, is proof that it pos- 

 sesses decided merit in some cases. No thoroughly satis- 

 factory'tests have been made upon the relative merits of steam 

 and hot water for modern greenhouse-heating. 



In greenhouse construction there is an evident tendency to- 

 wards simplicity, which is itself a positive indication that the 

 greenhouse business is becoming more practical. The ten- 

 dency is towards large to very large glass and light frames. 

 Glass as large as 20 x 3° inches is sometimes used for roofing. 

 Iron rafters are coming into frequent use, because of their 

 durability and little obstruction to sunlight. Iron-frame and 

 slate-top benches are making their way from conservatories 

 into forcing-houses and propagating-pits. 



Some of the recent movements in greenhouse construction 

 in France are discussed as follows by Maximilien Ringelmann* 

 in a report upon horticultural arts and industries as displayed 

 at the Exposition of the National Society of Horticulture of 

 France : 



"One division of the general exposition embraced horti- 

 cultural arts and industries. It was divided into four sec- 

 tions. The first section included greenhouses, sash, frames, 

 screens, garden-matting, and apparatus for heating. There 

 were 55 exhibitors. The second section included tools and 

 machines, sprayers, garden furniture, etc. There were 40 

 exhibitors. The third section comprised arbors, rustic con- 

 structions, kiosques, etc., there being 48 exhibitors. Finally, 

 65 exhibitors entered the fourth section, which embraced va- 

 rious arts, pottery, basket-making, cutlery, scales, bric-a- 



*Revue Horticole, 1891, 277. 



