1873.] LOW NIGHT TEMPERATURE. 205 



keep our houses for tropical plants and fruits by day, as they generally are kept 

 at the present time, we would have a very poor result ; and so long as day tem- 

 peratures are kept as they generally are, it would not be very good practice. 

 Of course I am speaking of plant-stoves and forcing-houses — the greatest con- 

 sumers of coal, andwhich require the highest temperature. We never have, as a 

 rule, aimed at a strictly tropical day-heat. Indeed it would in winter be all but 

 impracticable to do so. We have rather been contented with 50^ to 60° night- 

 heat, and from 60° to 70° day-heat, and lower in very cold weather, and higher 

 with sun-heat, which is such a scarce commodity with us from October till March 

 that it can enter but little into our calculations. A fall to 40° in the morning 

 sometimes occurs, but on such occasions the heat is got up 5° or more as quickly 

 as possible, as compeosation. The only perceptible harm I ever could detect in 

 going down to 40° happens to the flowers. I have long acted upon the theory that 

 a low night-temperature must have a corresponding high day-temperature, but the 

 middle course is the safest. In coming to summer treatment, say from March 

 to September, this is the time in a good many cases that the coal bill may 

 be lessened, not only with no evil result, but with much positive advan- 

 tage. It is the proper balancing of heat and moisture at the roots and in the 

 air that gives us the most luxuriant growth. Nothing can operate so much 

 against a growing plant as hot, dry, hard, thin air. Do we as a rule utilise sun- 

 heat as we ought ? I rather think not. The usual practice is to do all, or nearly 

 all, the watering at night and morniug, which is all right as far as it goes ; but 

 something more remains to be done, and that is to feed the air properly with 

 moisture during the day when the houses are hottest. It is far more needed 

 then than at any other time, because it mixes with the hot air, and is then made 

 into proper food for the plants. 



Moisture and heat must — 'if I may use a homely phrase — go hand in hand if 

 you wish a steady luxuriant growth. It is far too often the practice to allow 

 the best and fattest of the air to escape by the top ventilators, before it has 

 given any material assistance whatever to the plants. There is no greater 

 inconsistency in practice than having heat in our power, and allowing it to pass 

 away without first having secured all that is valuable out of it. I would say 

 that far too much air is given during sunshine. The roofs of our houses, as a 

 rule, are pitched at the best possible angle to catch as much of the sun as we 

 can, which soon riins up the thermometer to tropical heat. This is the golden 

 time for plenty of moisture in the air. But what do we do ? We ojien top and 

 bottom ventilators, until we have it down to 80° or 85°. Why not give plenty 

 of moisture to the air, and allow it to run up other 10° or 15°, and then the 

 plants would enjoy the benefits of a cool temperature at night ? The air should 

 always be circulating ; never at rest, but always moving — of course more by day 

 than night. A high thermometer is no indication of itself that growth is i)ro- 

 gressing according to the heat. It is only when duly tempered by moisture 

 that it can be most acceptable to the plants. What I woidd propose would be 

 something like the following : To collect in a tabular form all the information 

 from your numerous correspondents on the points at issue, which, to be of any 

 available use, must to the minutest degree be trustworthy. Say, to note the 

 outdoor thermometer and barometer three times a-day ; the same with indoor 

 thermometer; also the quantity of water made use of, and how; with the weight 

 of coal consumed per day or per week, and what other conditions you might 

 think proper to impose ; with notes on the various stages of growth up to 

 maturity. If you could only set this machinery in motion, it would, in my 

 opinion, lead to a great reform, although it may be years before we arrive at 



