194 MANUAL OF AMERICAN GRAPE-GROWING 



may be blistered by the sun's rays being focused through 

 defective spots. 



Light, heat, moisture and good ventilation are all required 

 in the grapery. Brick or stone are preferable to woodwork, 

 as heat and moisture in the grapery are quickly destructive 

 to wood foundations. If wood is used, only the most durable 

 kinds should enter into the construction of the house. The 

 under structure of masonry or of wood should be low, not higher 

 than 18 inches or 2 feet before the superstructure of glass 

 begins. The grapery must be well ventilated. There must 

 be large ventilators at the peak of the house and small ones 

 just above the foundation walls or in the foundation walls 

 themselves. The ventilation should be such that the house 

 can be kept free from draughts or sudden changes of tempera- 

 ture, as the grape under glass is a sensitive plant, and subject 

 to mildew. Plenty of air, therefore, is an absolute necessity 

 to the grapes, especially during the ripening of the fruit. The 

 lower ventilators in graperies are seldom much used until the 

 grapes begin to color, at which time the new growth, foliage 

 and fruit are hardened, but from this time on upper and lower 

 ventilators must be so manipulated that the houses are always 

 generously aired. 



Grapes can be forced in cold houses without the aid of arti- 

 ficial heat and formerly these cold graperies were very popular ; 

 but in the modern houses for growing this fruit, artificial heat 

 is now considered a necessity, even though the heating appara- 

 tus may seldom be in use. For a finely finished product, a 

 little heat to warm the room and dry the atmosphere may be 

 absolutely necessary at a critical time, this often saving a 

 house of grapes. Of heating apparatus, little need be said. 

 Standard boilers for heating greenhouses with either steam 

 or hot water are now to be purchased of many designs for almost 

 every style and condition of house. Since the grapery seldom 

 requires high heat, hot water is rather to be preferred to steam, 



