86 



advantageously used in many cases in starting and 

 preparing plants to be finally removed to the field. 

 The object to be kept in mind in the construction 

 of a greenhouse is first of all the securing of the 

 maximum amount of light. 



It must be remembered that plants are to be 

 grown during the short days of the year, and when 

 the maximum of cloudy weather is to be expected. 

 The house must be so constructed as to make pos- 

 sible the economic maintenance of a proper degree 

 of heat. Provision must be made for a cheap and 

 adequate water supply. One must provide for ven- 

 tilation without serious loss of heat and without 

 sudden and violent changes of temperature. 



In order to secure the maximum amount of light 

 in the greenhouse it is necessary to use as light 

 material as possible in its construction. Sash bars 

 of cypress or some other lasting wood are usually 

 employed. These bars or strips are properly rab- 

 beted to receive the glass and are usually from ij4 

 to 2 inches in depth by Ij4 to ij4 inches in thick- 

 ness. When possible, they should be cut the length 

 of the house slope. This can usually be done in 

 the smaller houses, but in some of the larger houses 

 now being constructed one and even two laps are 

 often necessary. 



Gas pipe is preferable for supports of all kinds, 

 because of its small size and great strength. Less 

 light is eliminated than by the use of many other 

 available materials. 



The pitch of the roof is a matter of great Im- 

 portance and this will vary considerably with 

 the latitude in which the structure is to be 

 located. During the winter months, when the green- 

 house is in most active use, the sun is at the lowest 



