Notes on Greenhouse Plants, S^c. 303 



amount of moisture is necessary to counferact the aridity of 

 the heating apparatus. Plants suffer much from the drying 

 nature of the heat in severe weather. In summer, evening 

 watering may be beneficial in cooling the system and induc- 

 ing temporary repose, after the excessive heat of day. We 

 have an indistinct recollection of reading a paper by the late 

 Andrew Knight, on this subject, where he stated his opinion 

 in favor of syringing with very cold water towards evening. 

 Our own experience, after many trials of different methods, 

 has induced us to adopt morning watering at all seasons. 

 By using water freely about the house in the early part of a 

 hot day, the atmosphere becomes charged with moisture, and 

 the house is much easier kept cool and agreeable during the 

 remaining portion of the day. Towards evening the syringe 

 can be used in distributing water on the floor and all vacant 

 places of the house, and also on all plants not in flower. 

 The same treatment is practised in winter only when artifi- 

 cial heat is in requisition ; otherwise, the drier the air, the 

 less danger from cold. 



Independent of the physical advantages of early watering, 

 there are chemical changes connected with the practice, 

 which we think are not sufficiently understood or recognized. 

 Plants are constantly extracting moisture from the soil by the 

 roots, and parting with it by the leaves. The leaves, when 

 exposed to the action of light, decompose carbonic acid, 

 ammonia, and other matters present in the soil, from which 

 organic matter is formed. The amount of water taken up 

 by the roots varies with the moisture in the soil, the state of 

 the atmosphere, and the species of plant. During hot, dry 

 nights, much watery vapor is parted with by the leaves. 

 It is evident, therefore, that the moisture given off at night, 

 carries with it a considerable amount of gaseous matter col- 

 lected from the soil, without benefit to the plant, since the 

 presence of light is necessary to the performance of those 

 chemical functions which digest and retain the substances 

 required to develop and extend the structure of plants. Hence 

 we may consider the above as an important argument in 

 favor of early watering. 



