unCHIDS : HOW TO GROW THEM SUCCESSFULLY. 173 



register over saturation point in the Odontoglossum house ? In such a house 

 with a north aspect it is a simple matter (at least in winter) to remain at 

 saturation point, and that does not seem to me to be moisture enough in the 

 air for this class of plants, as they .dry so quickly, owing I suppose to the 

 amount of ventilation they get. Then the Cattleya house seems to me to do 

 better when never quite reaching saturation point. Here we live on the top of 

 a hill, and the air is very pure and the sunlight strong. The Cattleya house 

 to-day (January 8th) has reached 90 of sun heat, and it is impossible to 

 ventilate too freely as there is a cold north wind ; of course the hygrometer 

 under such conditions registered about 8 or 9 of dry heat. It would be a 

 great help if you could let me know what is best to be done under such 

 circumstances. I do not like to shade yet, as I imagine sun heat is so very 

 beneficial just now to the Dendrobes, which are resting in the Cattleya house. 

 The East India house, where I keep most of the Cypripediums, never ranges 

 more than 3 from saturation point, and being next to the Odontoglossum house 

 it does not get so much sun as the Cattleya house. I have used leaves on the 

 lower stage as you recommend, and I have a long narrow tank containing 

 four inch pipes and is kept full of water to counteract the effects of the large 

 hot water pipes above, so that I have moisture above and below the hot water 

 pipes, also a huge tank along the centre of each house below the centre stage ; 

 still I find it hard work in bright weather to keep the Cattleya house at all 

 moist. If you could state the variations near about what the hygrometer 

 should register for the different months, it would be a great help to many. 



REPLY. The hygrometer is an instrument, the want of which in the 

 cultivation of plants is so little felt amongst gardeners that very few possess 

 them, and with that few the hygrometer may often be seen doing duty as a 

 thermometer only, the wet bulb not being kept supplied with moisture. It is 

 difficult to get the atmosphere beyond saturation point, and it is not advisable 

 to try to do so. In the Odontoglossum house saturation point should be 

 generally attained, or the nearer to it the better during the spring, summer, 

 and autumn months. It is not possible to maintain it if the house is properly 

 ventilated, and the hygrometer will stand about 3 below saturation point. In 

 the winter it is easy to keep the cool house at saturation, but it is better if it 

 remains for the greater part of the time at 1 or 2 below. In the other houses 

 damp down freely, but the hygrometer will never stop at saturation long, nor 

 is it advisable. Air is an important factor as well as moisture, and when air is 

 admitted properly the wet bulb will stand at from 3 to 5 below the dry one ; 

 if lower, then there is not enough moisture in the house. In these houses 

 during the winter I always damp down when the hygrometer shows 3 to 5 of 

 evaporation, unless for a short time at mid-day. If the directions given in the 

 Calendar of Operations for each month are acted upon, the hygrometer should 

 register these figures. Water tanks are invaluable for the storage of rain water, 

 but practically a body of water is useless for producing moisture unless made, 

 by the aid of hot water pipes running through it, warmer than the tempera- 

 ture of the house, ^Then moisture is produced in the form of steam, but this is 

 a method I do not recommend, for if not managed very carefully too much 

 steam is generated, which is very injurious. The best way to cause evaporation 

 is to frequently syringe the paths, stages, and wall. 



