410 Report of Farmers' Institutes 



Houses 



Simple greenhouses are sometimes built from sash, but the 

 newer types are built with especially designed frames. The 

 cheapest form of construction for large areas consists in ridge-and- 

 furrow houses, 15 to 30 feet wide, with posts at gutters and, in 

 the wider ones, at the ridge. Such houses are very widely used 

 and are giving excellent results; however, those who have capital 

 available and are interested in permanency are showing an increas- 

 ing tendency toward wide houses built single with substantial iron 

 frames of rafters and trusses. The woodwork of such a house is 

 practically permanent if it is kept well painted. Even after it 

 has deteriorated, it can be replaced without entirely rebuilding 

 the house. 



Heaiing System 



Greenhouses are heated in various ways, generally by means 

 of steam or by means of hot water under natural or forced circula- 

 tion. The tendency is to use hot water under gravity circulation 

 for the smaller ranges and steam or hot water under forced circu- 

 lation in the larger areas where it is necessary to employ a night 

 fireman. . 



Fertilizer 



Fertility in greenliouses is maintained almost wholly by means 

 of heavy applications of stable manure. The soil is regarded as 

 permanent and is not ordinarily changed, as is the case with most 

 floral houses. The fact that it is not subjected to the rigors of 

 winter frequently renders it necessary to sterilize the soil to keep 

 it free from certain pests, chief among which are certain fungi 

 and minute worms known as eelworms or nematodes. 



Water Supply 



Water is supplied in such quantity as to meet the requirements 

 of the plant for actual growth of new material and for maintaining 

 the body activities of the plant. An undersupply results in 

 checked growth with increased time for crop production and poor 

 quality. An oversupply results in an unhealthy type of growth 

 and favors the development of crop enemies, as well as delaying 

 maturity and perhaps bringing about actual breakdown of plant 

 tissue. 



