72 MASSACHUSETTS HORTICULTURAL SOCIETY. 



should receive one additional coat. It will be found very advan- 

 tageous, if a small percentage of oxide of zinc is mixed with the 

 white lead used for painting the inside of the houses. This 

 imparts a much brighter whiteness, and prevents the growth of 

 the gray fungi which adhere to interior surfaces painted with the 

 lead only, and which give the inside of the house a dirty and 

 untidy appearance after a short season's use. This mixture is 

 used now very largely in Government work, and also in the 

 greenhouses at the Executive Mansion at Washington, it being 

 there, I believe, that the original experiments were first made, and 

 the good results discovered. 



Ventilation. Ventilating conveniences play a very important 

 part in the furnishing of a greenhouse, the usual system being to 

 have a continuous line of sash about three feet deep along one or 

 both sides of the ridge, and also a similar line below the gutter or 

 eaves line, these being operated by some suitable mechanical 

 means ; preferably by the well-known worm and wheel apparatus. 



Heating. The heating apparatus plays the most important part 

 in the furnishing of a greenhouse. There are three systems of 

 heating in use ; namely, first, by means of hot-air flues ; second, 

 by means of circulation of steam through coils of pipes ; third, by 

 means of a circulation of hot water through coils of pipes. The 

 heating by flues is a very primitive method, but is often resorted 

 to in consequence of its small first cost, but its cost of mainte- 

 nance is greatly in excess of that of either steam or water heat, 

 and its results leave much to be desired, as the flues will become 

 leaky, and allow dust and gas to escape into the greenhouse, and 

 destroy all but the hardiest stock. Steam heat comes next in the 

 order of merit ; it also has the advantage of comparatively low 

 first cost, but also has the disadvantage of being costly of main- 

 tenance, both in the matter of fuel, attention, and repairs. This 

 systeiu is largely in use, and finds many advocates. Hot-water 

 heat, while entailing greater first cost, is the system in general 

 favor, being economical in fuel, requiring very little attention, 

 entailing no cost for repairs, and at all times, when there is any 

 fire under the boiler, being positive in its action. Thus far, it 

 must readily be admitted that the hot-water system of heating is 

 the most desirable, but we have yet to consider the effects on 

 plant life. Steam heat, on account of its intensity, has a tendency 

 to dry the atmosphere of the house to the injury of the plants, 

 but this can be easily counteracted, by means of frequent and 



