6 GREENHOUSES 



Forcing houses seem to have had their 

 origin in an attempt to grow in the northern 

 countries of Europe fruits such as the orange 

 and grape, which were grown to such perfec- 

 tion in the countries to the south. Thus in 

 England the grape vine is hardy, but the 

 summers are too cool and the seasons too 

 short to ripen the fruit to perfection. This 

 led to the training of the vines on the south 

 side of buildings and walls that they might 

 receive more fully the light and heat of the 

 sun. Later there was conceived the possibil- 

 ity of still further protecting them by the use 

 of glass sash leaned against the wall. From 

 this it was an easy step to the building of 

 a rather permanent framework close to the 

 walls, on which glass sash were placed when 

 required, forming a closed house. Sometimes 

 the walls were made hollow and slow fires 

 built within them to give additional heat. 

 Finally the idea of heating the air instead of 

 the walls on which the vines were trained 

 resulted in the building of brick and stone 

 stoves or fireplaces within the glass enclos- 

 ures. These houses were never intended for 

 winter use, but simply to make the summer 

 and fall conditions similar to those farther 

 south. 



