THE GRAPE VINE. 



627 



the rafter, over the whole surface of the roof, 

 upon gable or suspended trellises, sometimes 

 12 inches from the glass, and from that to 20, 

 and in some few instances at even a much 

 greater distance (vide vol. i., fig. 403). The 

 object of training under the rafter is to allow 

 the light to have full influence on the foliage 

 and fruit, which no doubt it has much more 

 than when the whole roof surface is entirely 

 covered. How far, however, this is of advan- 

 tage to the fruit has been questioned by some, 

 as elsewhere noticed. Eighteen or even twelve 

 inches may be sufficient for small-leaved vines 

 with short foot- stalks, but twenty is a much 

 better distance for large-growing leaves and vines 

 full of vigour; and this is the more necessary 

 where large panes of glass are used, because at 

 that distance the leaves have room to develop 

 themselves fully without coming in contact with 

 the glass; and as air is more freely admitted 

 around them, the leaves are much less liable to 

 be scorched by inferior glass, or lenses forming 

 on that of even good quality. 



Producing a long supply by successional houses. 

 — It has been suggested, as the most certain plan 

 of securing this end, to have six houses, beginning 

 to force, the first at the end of October, the 

 second on the first of December, the others on 

 the first of January, February, March, and April ; 

 while others have attempted the same thing 

 with half the number, beginning the first in 

 November, the second in February, and the third 

 in April. 



/Syringing is considered a most essential 

 operation in vine culture by some cultivators, 

 while others scarcely recognise it as of the least 

 importance after the buds have broken. It is 

 perhaps best to take an intermediate course, and 

 consider that both are acting on the extreme. 

 Mr Johnstone, in " The Gardeners' Monthly 

 Volume," remarks : " If sufficient atmospheric 

 moisture is provided by means of a permanent 

 character, little syringing will be needed. It may 

 be practised with benefit, during the time the buds 

 are swelling, two or three times a- day. When 

 blossoming comes, it must be altogether omitted. 

 It may be resumed again until the berries be as 

 large as peas, when it will be better entirely dis- 

 pensed with, taking care to provide plenty of at- 

 mospheric moisture in lieu of it. The desirable 

 amount of moisture in the air of the vinery is 

 by no means arbitrary, but ought to be regulated 

 according to the rule pointed out by nature. 

 Her law is that the moisture of atmospheric air, 

 unaffected by accidental causes, is proportional 

 to its temperature, the moisture increasing with 

 the heat. The exceptions offered by the sirocco 

 and other hot dry winds have their accidental 

 origin from passing over arid torrid plains, in- 

 capable of affording moisture to the passing air. 

 The consequences such winds bring upon vege- 

 tation are well known to be destruction of its 

 foliage, and in many instances death. Air at 

 rest, as in a hothouse, does not absorb moisture 

 so rapidly as air in motion ; therefore, if the 

 whole area of its floor was a tank of water, the 

 air confined within the house would never be so 

 saturated with moisture as air at the same 

 temperature passing over water, moist earth, 



and vegetation, as in the ordinary course of 

 nature. To obviate this, gardeners promote the 

 diffusion of watery vapour through the air of 

 their hothouses by placing pans of water upon 

 the flues, by having open gutters of hot water 

 cast upon the hot-water pipes, and by even admit- 

 ting jets of steam. The difficulty attending all 

 these processes is to have the amount of vapour 

 in a natural proportion to the temperature of the 

 house. A little inequality is not of much con- 

 sequence, but, other treatment being correct, 

 the nearer to the dictate of nature so much the 

 nearer will the plants be to a state of best 

 vigour." 



" A consequence of air being duly impregnated 

 with moisture is, that evaporation of water from 

 a given surface exposed to that air proceeds 

 slowly, shown by its causing but little cold." 



" The easiest mode of ascertaining the differ- 

 ence between the temperature of the air and an 

 evaporating surface is by having two equally 

 graduated thermometers hanging in the hot- 

 house, with the bulb of one enclosed in a piece 

 of thin muslin. Upon moistening this with 

 water of the house's temperature — made so by 

 keeping it in the house— the number of degrees 

 this causes the mercury to sink will be the 

 difference between the air's temperature and 

 that of an evaporating surface. In the winter 

 months the gardener may be satisfied that the 

 air has the desirable moistness, if that difference 

 be not more than 6°, and during the summer 

 months 3°. This is much less than the differ- 

 ence found by observation in a tropical climate, 

 but there the evaporation was promoted by 

 exposure to a free circulation of the air." 



" Although syringing and steaming, duly regu- 

 lated, are unexceptionable practices occasionally, 

 yet, as before observed, they are not to be 

 depended upon solely as the means of keeping 

 the air of the hothouse in a proper state of 

 moisture, in conformity with the natural laws 

 already pointed out. Gardeners know this from 

 their experience, and have adopted, consequently, 

 several modes of keeping the moisture of the 

 air always accordant with its temperature." 



Many depend on damping the floor, walls, 

 and foot-paths of their vineries, for insuring the 

 requisite amount of atmospheric humidity, and 

 some have combined with this the diffusion of 

 fertilising gases at the same time. This has 

 been effected by watering with highly enriched 

 liquid, by setting vessels of it in various parts of 

 the house, by sprinkling the foot-paths with 

 ammoniacal liquor — but this is objectionable on 

 account of the disagreeable appearance; and 

 hence Mr Milne, an intelligent cultivator, has 

 placed it in three tin cans, in a house 42 feet 

 long, and found that in two days the liquid had 

 wasted one-third of its bulk, the residue changing 

 to a thick substance like coal-tar. It might be 

 injurious to apply much of this to the roots of 

 the vines; besides, it has been found that its 

 fumes did not become disengaged so readily 

 when sprinkled on the soil as when thrown 

 upon hard non-absorbing borders. The advocates 

 for non- syringing should bear in mind that the 

 foliage of plants, in even the best regulated 

 houses, is liable to become covered with dust, 



