GLASS STEUCTURES AND APPLIANCES. 



165 



And thus it comes to ptxss that while these may 

 need damping- down fiill half a dozen times a 

 day, cool green-houses and conservatori-es may need 

 none, and in winter too much care can hardly 

 be exercised to keep the paths and stages dry. In 

 winter, too, even in tropical temperatures, little or 

 no damping down may be needed, as there is no sun 

 to dissipate the moisture, and the plant may need to 

 be forced to rest or ripen in a dry atmosphere. But 

 during the growing season persistent eiSorts to 

 charge the atmosphere with aqueous vapour must 

 be made. The phrase " damping down " is hardly 

 descriptive of the practice, though its object is really 

 to raise, not the dust, but aqueous vapour, which is 

 pure water, free of dust and dirt of every sort, and 

 hence one of the greatest merits of the practice. 

 Sprinkle paths, shelves, stages, walls, once, twice, 

 thrice, or oftener a day, and the air is charged with 

 a sufficiency of pure vapour to supply the top wants 

 of the plants. Other means are also used, such as 

 overhead syringing at 7 a.m. and 5 p.m., sprinkling 

 of roof, rafters, front and back walls, &c., in pursuit 

 of the same object, thus charging the atmosphere 

 with vapour. Another ingenious method is also 

 employed; at times a small boiler, or covered pot, 

 with jet or pipe with tap attached, is so placed that 

 steam can be distributed into the atmosphere when 

 wanted. This obviates the necessity of overhead 

 syringing ; and, if a small jet is used, the heat of the 

 steam does no harm to Orchids in full growth. And 

 yet another plan, of employing vital distributors 

 of aqueous vapour, as beautiful as useful, is fre- 

 quently employed. The front, back, or end walls 

 are clothed with Ferns, Selaginellas, or other droop- 

 ing or creeping plants, and these raise and dis- 

 tribute much aqueous vapour by simply growing, 

 generating it with twofold power when their leaves 

 a,nd branches are moistened v^^th water. 



Watering. —This refers to the roots, and in 

 answer to the question, How often should these be 

 watered ? the only answer is, When dry. No other 

 is possible, unless it would lead to the ruin of the 

 plants. Water only and always by condition, never 

 by time. Look over the plants daily, ov twice a day 

 in the growing season ; test the water- wants of the 

 plants by the eye, if thoroughly experienced, and by 

 the following tests if not yet perfect in water know- 

 ledge of plants — weight, colour of surface, ring of pot, 

 state of the leaves. Those accustomed to handle pots 

 of given sizes can tell in a moment by their weight 

 if the soil is dry. A light-coloured surface mostly 

 indicates a need of water. A wet pot has no ring in 

 it — it sounds as dead as a log of wood ; a dry one 

 sounds as clear almost as a bell when a willing knuckle 

 is used vigorously on its sides. The flagging of the 



leaves is also a test of drj-ness, though less certain 

 than either of the others, for this may arise from 

 bright sunshine succeeding shade, and also from 

 a saturated condition of tissue, resulting from an 

 excess of water at the roots. 



How Much Water to Give.— This must 

 vary with the size and the character of the plant, 

 and the relative size of the pot to the same. Of 

 course the larger the plant the more water in 

 proportion, though the larger the pot in contrast 

 with the plant, the less. Plants with large and 

 porous leaves will also need larger supplies than 

 those with smaller and harder foliage. Sufficient 

 should in all cases be given to reach every rootlet 

 and gTain of earth. For such waterings are thorough, 

 and therefore safe, and not another drop should be 

 given again until the roots manifest some or all of 

 the symptoms of dryness. 



These are what are termed routine, that is, regular 

 waterings, and they apply to all jDlants in pots, 

 whether in-doors or out, in a trojDical or temperate 

 temperature. 



Exceptional Waterings. — These apply espe- 

 cially to Orchids, and it must not be forgotten that 

 the withholding of water is the chief means of 

 maturing their growth, compelling them to rest, 

 and thus insuring their health, and augmenting their 

 floriferousness. These forced rests through drought 

 for special purposes are, however, quite outside 

 normal waterings, though similar considerations 

 limit the supplies to most stove plants in the late 

 autumn and throughout the winter. The rate of 

 growth determines, to a great extent, the amount of 

 water utilised ; and, hence, a state of maturity or 

 semi-rest must needs prove a season when less water 

 is needed. 



The Giving of Air. — One of the things that 

 surprise the amateur is the care and skill bestowed 

 on the many contrivances invented for the prompt 

 and almost immediate giving and withdrawal of air 

 from plant-houses. Their first and chief idea of a 

 plant-house is that of a closed structure, and they 

 cannot understand why all this labour and expense 

 in making them open and close. But a winter's 

 experience in the management of an old-fashioned 

 plant-house, and a record of the time taken up in 

 opening and shutting ventilators daily, would alter 

 the amateur's opinion. All this, however, will be 

 found described and illustrated in a separate chapter. 

 Here it is only needful to refer to the time to give 

 air, and the amount of air to give. As to the time, 

 by opening the ventilators so soon as the sun has 

 raised the temperature five degrees or so, we give 



