524 



THE GARDENER'S ASSISTANT. 



and often of a nature calculated to exclude 

 light. There is nothing more simple or effec- 

 tual than a hinged light on each side the ridge, 

 about 2 feet in depth, worked with the usual 

 lever and screw gearing; this allows air to be 

 given even in wet weather, and at whichever 

 side is most favourable; it also admits of abun- 

 dant ventilation in hot weather. Further de- 

 tails of greenhouse construction will be found 

 in chapter xvii, p. 199. 



Air. — Plants grown under glass necessarily 

 do not receive nearly so much fresh air as they 

 get in their native habitats. Much has been 

 written on the principles of ventilation for plant- 

 houses, and yet nothing is more common than 

 to see them treated in respect of air in a way 

 that renders all other attention futile, it being 

 either withheld at times when it should be 

 admitted freely, or given in a continuous 

 routine sort of fashion from a certain hour 

 in the morning to a given time in the even- 

 ing, regardless of the state of the weather or 

 season. It is impossible for any plant to make 

 favourable progress when subjected to cold 

 draughts, yet we too often see, even in the 

 spring, when young tender growth is in course 

 of formation, the front-lights of plant-houses 

 open right in the face of a keen cold wind that 

 cripples the young leaves. Where, however, 

 the side-lights of the house are made to open, 

 as already advised, air can always be admitted 

 on the side opposite to the direction from 

 which the wind blows. The quantity of side 

 air admitted must be regulated more by the 

 state of growth the plants are in than by the 

 temperature of the air, either within the house 

 or externally. The temperature of a green- 

 house in spring, when plants are making young 

 growth, may be allowed to rise a few degrees 

 too high rather than admit cold air in large 

 volumes. In our fickle climate we often get 

 several descriptions of weather in a single day. 

 The careful cultivator will notice these changes, 

 and regulate the admission of air accordingly, 

 always bearing in mind that when the houses 

 are closed in the after part of the day the 

 greatest amount of growth is encouraged; 

 later in the season, as the young growth be- 

 comes solidified and ripened, more air will 

 be required in the day, as well as at night; 

 but never, even when the wood and leaves are 

 fully matured, should any plant be subjected 

 to a keen draught, which is always more or less 

 injurious. 



Temperature. — The large variety of plants 

 that are grown in a single greenhouse cannot 



be provided with any special conditions which 

 in nature they would enjoy, and this is par- 

 ticularly true in regard to temperature. Many 

 greenhouse plants are not perceptibly injured 



I by a degree or two of frost. On the other 

 hand, many are seriously injured by being 

 excited into premature growth by too high a 

 temperature in winter when the other condi- 

 tions are most unfavourable. To prevent this 

 a low temperature is preferable, and the night 



; temperature during winter for a general col- 

 lection of greenhouse plants should be from 

 40° to 45°, or even 35° to 40° if the weather be 

 very cold. The temperature during the day 

 should be correspondingly low. 



Watering. — This is by far the most import- 



' ant operation connected with the cultivation 

 of plants in pots. The necessity for con- 

 tinuous attention and watchfulness as to the 

 requirements of each individual plant where 

 large collections are grown cannot be realized 

 by any but those who have had experience 

 in the matter. A deficient or superabundant 

 supply of water probably causes the death of 

 more pot plants than all other causes put to- 

 gether. It is of all matters connected with 

 plant culture the most difficult to explain. 

 Only by patient observation of the require- 

 ments of each particular species can the neces- 

 sary knowledge be obtained. 



Acquaintance with the conditions as to water 

 under which a plant is found wild may be 

 helpful, although it may not be advisable to 

 try to imitate them. It may be taken as a 

 rule that the finer the roots possessed by any 

 plant the more impatient it w T ill be of a defi- 

 ciency or excess of water. On the other hand, 

 thick, strong-rooted plants are generally able 

 to support these extremes. Greenhouse plants 

 of all kinds, when they receive water at all, 

 require sufficient to thoroughly moisten the 

 whole of the soil. Only aquatic or bog-plants 

 require more than this; consequently, there is 

 no great amount of knowledge required to 

 know in watering how wet the soil ought 

 to be made. The important point is to know 

 what degree of dryness in the soil should be 

 permitted before water is given. Many deli- 

 cate-rooted, hard -wooded plants are killed by 

 a single mistake in watering. The condition 

 of the soil should be studied, and of course the 

 condition of the plant, whether it be in vigor- 

 ous growth or comparatively at rest, must also 

 receive attention. 



Soils. — The principal of these are: — peat, 

 both bracken and heather used for hard- wooded 



