FUMIGATION OF GREENHOUSES 



65 



giving the number of cubic feet in the upper portion of the green- 

 house, which, added to the number of cubic feet in the lower 

 portion, gives the capacity of the greenhouse in cubic feet. 



Many greenhouses have the sides unequal and the slopes of 

 the house unequal, as shown in figure 90. In such a- greenhouse, 

 one must multiply the height AB by the width of the rectangular 

 portion A BIG, which width is AG, G being a point immediately 

 underneath the highest portion of the roof. The same is done 

 for the rectangular portion DEGF. We then have two triangular 

 portions still to compute. Multiplying CI by IB and dividing 

 by two gives the number of square feet in the portion CIB. The 

 same is done for the triangle DCF: that is, DF is multiplied by 

 CF and divided by two. 



The number of square feet in these four sections are then added 

 together to give the sum-total of square feet in the end of the 



FIG. 90. Diagram showing roof with unequal sides. 



greenhouse. This sum is now multiplied by AH to get the cubic 

 feet in the house. 



Amount of Chemical. After having carefully estimated the 

 number of cubic feet, the next point to determine is the amount 

 of the chemicals to be used. This varies according to the plants 

 which are present. Some plants are more susceptible to cyanide 

 gas than other plants, and where there are a number of different 

 plants in the same house the amount of material to be used should 

 be such that it will not injure the most tender variety. 



Two other factors which are most important are the tempera- 

 ture and the humidity in the house. Plants are always more 

 readily injured in a house where the temperature is low, say 60 

 degrees, than they are when the temperature is high, as, for example, 

 70 to 80 degrees. The more moisture in the house the more apt 

 the plants are to be injured, so that the house should be just as 

 dry as is possible, considering the plants which are in it. 



