122 VEGETABLE GARDENING 



pairs in other types of construction. With proper care 

 and painting- the wood parts in a well-built nouse will 

 last 25 years, and they could then be renewed at :-. cosr 

 which would not be burdensome to a grower who had 

 harvested profitable crops for a quarter of a century. Iron 

 pipe, concrete and thoroughly dried cyp: ess are the most 

 important materials needed in the construction of a mod 

 ern commercial greenhouse. 



176. Semi-iron type of construction. This is by far 

 the most popular form of construction. The walls are 

 usually concrete, and the 2-inch pipe posts which support 

 the roof of the house are often embedded in the concrete. 

 If provision is made for walks or alleys along the walls 

 in the greenhouse the posts should extend at least 6 feet 

 4 inches above the ground level. All purlins, braces and 

 interior posts are made of iron pipes. The construction 

 is of such a character that it is easily possible to replace 

 decayed wood parts without disturbing the pipe posts, 

 purlins or braces. Walks, beds and benches of concrete 

 may be used if desired. Houses of this type are attractive, 

 serviceable and durable. Any local carpenter can build 

 them without difficulty, for nearly all wood parts are cut 

 to the right dimensions at the factory and blue prints are 

 furnished for the instruction of builders. 



177. Forms of greenhouses. Lean-to, side-hill, even- 

 span and three-quarter span are the distinct forms of 

 greenhouse construction. The lean-to house is the least 

 expensive type to construct, and it is often highly sat- 

 isfactory; but it is most useful when built as a lean-to 

 against a building" or wall running southeast and north- 

 west, where there will be practically no shading of the 

 plants. Lean-to houses are sometimes built along the 

 south side of larger greenhouses. While simple in con- 

 struction, they are not generally popular. 



Side-hill greenhouses are of various styles. Sometimes 

 they are built on the ridge and furrow plan with very 



