524 PRACTICE OF GARDENING. PART III. 



creases the heat to between 65 and 70 in the night. In August, he keeps down the thermometer to 75 

 or 80" in the day-time. In September, he returns to 65 in the night, and 70 or 72 with air in the day. 

 In October, he descends to 60 mornings and evenings, and 65 in sunshine. 



2773. Griffin differs from the above authors in recommending 60 as the heat proper for the pine in every 

 stage, not exceeding five or six degrees over or under. The bottom heat he considers proper, is from 

 90 to 100 degrees ! ( Tr. on the Pine, p. 60. 66.) 



2774. Baldwin does not mention at what temperature he keeps his succession-pit. 



2775. Covering at nights. Where succession plants are grown in pits or frames, this is 

 allowed on all hands to be most advantageous, by saving fuel, and preventing the risk of 

 an injurious cooling, which in pits and houses warmed by fire, and unprotected but by 

 the glass, will sometimes happen under the best management. Practical men recommend 

 mats, canvass, litter, &c. laid on the frames ; but a great improvement consists in keep- 

 ing the covering of whatever nature, and especially if of mats or canvass, at not less than 

 six inches on the principle experimentally illustrated by Dr. Wells in his Essay on Dew ; 

 Leslie, in his experiments on concentric cases (Essay on Heat), and derivable from the 

 fact known to scientific men (See Young's Lect.}, that heat follows the same general laws 

 as light 



2776. Speedily and Nicol complain of the great breakage of glass, by covering with mats, litter, &c. 



2777. Seton adopts portable covers of straw, arranged in the manner of thatch, and which may be com- 

 pared to the panels of reed fences or screens. They are formed on four laths, fixed at the same width as 

 the pit or frame one way, and not more than four feet apart the other. The chief advantage is, that as the 

 water runs off the thatch, the interior remains perfectly dry, so that there is no consumption of heat by 

 the creation of vapor in those parts which are near the glass ; " whereas mats, cloth, loose straw, and 

 other similar coverings become impregnated with moisture every night from dew, rain, or snow, and the 



evaporation which is thereby constantly generated, and greatly augmented by the contact of the warm 

 glass, causes a vast and continued drain of heat." Another advantage is the facility with which they may 

 be put on and taken off, and the little risk there is of breaking glass during these operations. (Hor't. 



glass, causes a vast and continued drain of heat." Another advantage is the facility with which they may 

 be put on and ' 



Trans, iii. 296.) 



2778. Air. Speedily considers a due proportion of air as essential to the goodness of 

 pine-plants. The want tf it will cause them to grow with long leaves and weak stems ; 

 and too great a quantity, or air given at improper seasons, will starve the plants, and cause 

 them to grow yellow and sickly. Little air will be wanted in winter ; but letting down 

 the glasses, even for a few minutes in the middle of the day, should never be neglected in 

 fine weather, to let out the foul air. This will cause the plants to grow with broad leaves, 

 and stiff and strong stems, provided they have room in the bed. Air may be admitted 

 all night in the hot season, care being taking that the glasses are left in such a manner as 

 to prevent the rain, in case any falls, from coming on the plants. ( Tr. on the Pine, 

 p. 751) 



2779. Abercrombie gives abundance of air in July and August, but with due caution the rest of the year. 



2780. M'Pfiail admits more or less air every fine day during spring and autumn, and abundance in the 

 summer months, which is also the practice of Nicol, Griffin, and Weeks. Baldwin seems to admit air 

 rather more sparingly than these gardeners. 



2781. Water. Speechly disapproves of ever giving a great quantity of water at one 

 time to the pine-apple plant, in any stage or at any season. Too much causes the mould 

 in the pot to run together and become hard and cloddy ; and, independently of this, 

 glutting a plant with water will rob it of its vigor, and reduce it to a weak state. 

 Hence, though keeping of plants too dry is certainly an error, it is not attended with the 

 same fatal consequences as the contrary practice. Watering the walks and flues, &c. 

 in an evening, in order to raise a kind of artificial dew, is in imitation of what takes 

 place in the West Indies, where no rain falls in the summer for many months together, 

 and the plants are wholly supplied with moisture from the dews. Gentle summer 

 waterings over the top are founded on this principle. " Plants lately shifted into the 

 pots, till their roots get matted, do not require so much water as before their shifting. 

 Plants that are in large-sized pots, in proportion to the size of the plants, do not require 

 so much water as plants that are under-potted. Plants that are in hard-burnt pots, made 

 of strong clay, do not require near so much water as plants in pots less burnt, and made 

 of clay with a good proportion of sand intermixed. The latter are greatly to be preferred. 

 Plants in a vigorous growing state require very frequent and gentle waterings. But 

 plants with fruit and suckers upon them require most of all. When plants are watered 

 over their leaves, it should be sprinkled upon them only till every part is made wet, 

 which may easily be distinguished, as the water immediately changes the color of them 

 to a sad green. As the leaves stand in different directions, the best method is to dash 

 the water upon them backwards and forwards, on every side of the bed. Summer 

 waterings should always be given late in an evening ; but in the spring and autumn, the 

 forenoon is the proper time. Less water should be given in moist than in dry weather, 

 for reasons already given. In winter, when water by accident falls into the centres of 

 the fruiting plants, it should immediately be drawn out, which may easily be effected by 

 the help of a tin pipe of about three feet in length, one end of which should be no bigger 

 than the small end of a tobacco-pipe." Pond or river water, or water collected from 

 the roof of the hot -house, and retained within the house till it has attained its tempera- 

 ture, is to be preferred. (Tr. on the Pine, 81, 82.) 



