MANAGEMENT OF GREENHOUSES 117 



may be so rapid that soft, succulent tissue is formed, 

 which is especially susceptible to disease; or a tempera- 

 ture unsuited to a species may produce a stunted growth. 

 The best plant and flower producers are those who study 

 their temperature conditions carefully and adapt them 

 to meet the needs of their crops. Varieties of carnations 

 have different temperature requirements and a variety 

 may not meet the expectation of the grower. The soil 

 and its moisture conditions may be ideal, but blooms are 

 small, short-stemmed and lacking in vigor. It is quite 

 possible that this particular variety needs a slightly in- 

 creased temperature, and if furnished, ideal blooms may 

 be produced. Fluctuating temperatures are extremely 

 injurious to plant growth, and a careless man in charge 

 of house temperatures may, in a short time, do much 

 harm to the vigor of a crop. 



91. Ventilating. Plants need an abundance of fresh 

 air, but changes in air contents of houses should not be 

 pronounced. It requires excellent judgment on the part 

 of the caretaker to admit sufficient fresh air to stimulate 

 plant growth without chilling the plants ; this is especially 

 true in small houses on bright, cold days in winter. 

 Xight ventilation is also important, for although plant 

 growth is not developing, due to the lack of sunlight, 

 nevertheless the air in the greenhouses should not be 

 heavily charged with moisture; and there should be as 

 pure atmospheric conditions by night as by day. This 

 often necessitates the application of a coil or two of steam, 

 even in warm nights in summer, and an elevation of the 

 ventilators so that surplus moisture in the houses may 

 not accumulate on the foliage, thereby favoring the 

 production of disease. 



The caretaker should know his houses and the amount 



