118 THE PRINCIPLES OF FLORICULTURE 



of air each requires under ordinary and unusual outside 

 weather conditions. In large houses, where the ventila- 

 tors are too high for the operator to observe just how much 

 air he is applying, a gauge of some description should 

 indicate the number of inches the ventilators are raised. 



The amount of air each species of plant requires, and 

 often the amount required by each variety, should be 

 known by the expert caretaker. Some species of orchids, 

 for example, naturally grow only on lofty trees. Such 

 demand a light, airy location in the houses. Other 

 species grow near the ground, in moister atmosphere 

 and often in diminished light. Certain other species of 

 tropical plants demand moist, shaded locations, while 

 others require full exposure to sunlight. An expert 

 plant-grower knows plants thoroughly and their require- 

 ments in every respect. The man in charge of ventilating 

 should be where he can reach his ventilating apparatus 

 easily and at all hours of the day. Frequently on cloudy 

 days in winter the sun bursts through the clouds and 

 in a very few minutes the temperature in the houses may 

 rise several degrees. Air must be applied so there will 

 be a gradual increase in temperature, rather than a sudden 

 change. Reverse conditions may occur by sudden cloudi- 

 ness, and especially by strong, unexpected gusts of wind. 

 Such variations in temperature bring about attacks of 

 mildew which often take a long time to eradicate. 



92. Firing. On large ranges it is necessary to employ 

 expert firemen for day service as well as for night service. 

 Such men thoroughly understand their business, and are 

 able to get the maximum amount of heat from the mini- 

 mum amount of coal. On smaller ranges, the fireman 

 often has other duties to perform, but the care of his 

 fires should always be his first consideration. Too rapid 



