184 REMARKS ON CULTURE OF ROSES IN POTS. 



perature maintained. In winter, when light is deficient, the nights 

 long and chilling, the days gloomy and cheerless, too little can 

 scarcely be made use of, provided that enough is given to maintain 

 vitality. As the spring advances, and more power is gained by the 

 sun — the source of light and heat; as the days lengthen and the 

 purer atmosphere transmits more readily the influence of that glorious 

 luminary, so will an increased proportion of moisture be recpiired by 

 the vegetable structure ; frequent syringings also become necessary, 

 not less to remove and dislodge insects than to clean away from the 

 breathing apparatus of the plants any encumbrance which may have 

 been deposited on it, and thus tend to impair its action ; the moisture 

 of the atmosphere should be maintained by sprinkling the heated pipes 

 frequently, and by the aid of" evaporating troughs" placed on them. 

 The application of moisture at the root should be sufficiently bountiful 

 to render soluble the food contained in the soil, and thus suitable to 

 be taken up by the spongeoles or feeding apparatus of the plants; 

 but it should, at the same time, be sufficiently limited to prevent the 

 medium in which that food is embodied from becoming soured or 

 soddened. 



Provided that attention is paid to keep the atmosphere free of ex- 

 traneous impurities, it cannot be maintained in too calm a state at the 

 time of the development of the leaf-buds and during the earlier stages 

 of growth ; the young shoots of roses are very succulent, and, toge- 

 ther with the blossoms, are very delicate and tender, and are therefore 

 liable to become seriously injured by exposure to a current of cold 

 air ; this injury should be particularly guarded against and avoided, 

 by keeping the house closed as far as may be practicable. Mr. 

 Knight has somewhere stated his belief, founded on his own observa- 

 tions, that it is by no means necessary to change the body of air in a 

 hothouse, by admitting cold air largely by opening the sashes, pro- 

 vided the internal atmosphere was kept free from impurities which 

 might arise from the soil or other causes ; a sufficient change of air, 

 he believed, would take place in a house kept closed, at least when 

 any considerable difference existed between the external and internal 

 temperature, through the various openings and creaks, which, though 

 scarcely discernible, are known to exist numerously enough in all 

 plant structures. This opinion is strongly confirmed by the success 

 which has attended a recent adaptation of the principle by Mr. Ward ; 



