138 Principles of Plant Culture. 



kept in living-rooms in winter. Such plants, especially 

 when few in number, rarely make satisfactory growth 

 and the lower leaves continually perish. Moistening the 

 air by evaporating water in the room or setting the pots 

 containing the plants upon a table, covered with moist 

 sand usually remedies the trouble. 



Insufficient moisture in the open air rarely occurs un- 

 less there is also a dearth of water in the soil. 



229. Insufficient Moisture in the Soil Retards Growth 

 both by reducing the tension of the cell-walls (63), and 

 by lessening the supply of food from the soil. The ten- 

 dency of drought is, therefore, to starve the plant. 



Plants that have been subjected to insufficient water 

 from the beginning usually suffer less from drought than 

 those previously well watered, because their root system 

 has become more extensively developed (112 J. 



230. Drought tends to Hasten Maturity, especially in 

 annual plants, since it favors flowering (135). Lettuce, 

 spinach, rhubarb etc., "run to seed" earlier if insuf- 

 ficiently supplied with water. Potatoes usually ripen 

 earlier in dry seasons than in wet ones. If the drought is 

 sufficiently severe or sufficiently prolonged, diminution 

 or failure of seedage results. 



231. Toughness of Plant Tissues Results from Drought. 

 The crispness and tenderness that give quality to salad 

 vegetables, as celery, lettuce, radish etc., due to a dis- 

 tended condition of their cell-walls, is largely wanting 

 when the water supply during growth has been insufficient. 



Insufficient water during growth injures the quality of 

 tobacco. Leaves thus affected have a peculiar spotted 

 appearance when cured, and do not u sweat" properly. 



