76 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



cause of trouble in a glasshouse is a faulty structure, which allows a 

 draught of cold air towards the heating apparatus. This draught induces 

 a local chilling on parts of plants, and non-resistance results. The 

 chilling blast often contains some spore which will set up disease on, 

 or in, the non-resistant part. From that point the disease spreads. 



A study of garden literature of over one hundred years ago suggests 

 that cultivators were less troubled with plant diseases than now— 

 their plants were hardier, no doubt because they did not force so much. 

 Cheap glass and chemical fertilizers have resulted in loss of stamina. 

 Lack of balance beitween light and heat is responsible for much. 

 For instance, it is comparatively easy to grow French beans for winter 

 use, but there are many failures, and one of the commonest causes is 

 that the grower does not appear to realize that he must regulate the 

 heat, which he has practically at his command, with the light, which 

 is a very variable quantity, especially from October to January, the 

 most critical months. When the light obtainable is deficient, the heat 

 must also be somewhat reduced, or weakly growth and fruitlessness 

 will result. Neglect of this extremely important point is the cause of 

 much trouble, especially when the autumn and winter is unusually 

 sunless. The market gardener too oTten endeavours to raise such 

 seedlings as Brussels sprouts under glass, and consequently gets weakly 

 plants. 



Judicious watering is immensely important, and, fortunately, 

 practical men know their work well in this connection. Using water 

 several degrees lower in temperature than the plants upon which it is 

 placed should be avoided. 



A suitable physical condition of the soil for the plant grown is 

 another subject too large to be adequately dealt with here. Expert 

 gardeners know the importance of having a firm soil for strawberries, 

 raspberries, carnations, onions, &c. In order to secure hardy, vigorous 

 broccoli which will be ready for use in, say, February, it is necessary 

 to have the soil very firm, notwithstanding that Brassicas generally 

 like a well-tilled and aerated soil. An undesirable physical and chemical 

 state of soil is occasionally caused by applying an acid fertilizer, like 

 superphosphate, to a soil deficient in lime. This is generally recognized, 

 but my experience is that the soil is frequently rendered acid or other- 

 wise unsuitable by the common method of putting dung dowm, say, two 

 spits deep, and especially so when it is put at the bottom of the spit. 

 Can we picture the root of a plant ramifying through soil containing 

 little organic matter, encountering what must appear to it to be an 

 almost impassable stratum of dung rich in the products of anaerobic 

 decomposition? Cultivators should try whether such plants as sweet 

 peas do better with a layer of rank dung at a foot or two beneath the 

 surface, or when the manure has become thoroughly incorporated with 

 the soil. I believe gardeners fifty years hence will wonder why this 

 common custom was practised so long. 



Without doubt the commonest predisposing cause to disease is 

 unbalanced plant-food. Our predecessors mixed their potting-earth 



