GREENHOUSE AND LABORATORY 39 



almost to the roof, which is composed simply of commercial 

 sash arranged to be raised for ventilation. All builders of green- 

 houses describe simple heating arrangements for small houses. 

 Sometimes the greenhouse is built on a roof or in a favorable 

 angle or court of the laboratory building, but such houses have 

 to contend with certain drawbacks, the labor of transporting 

 soil, pots, etc., up and down, the presence of gases rising with 

 warm air in the building, the difficulty of securing proper arrange- 

 ments for abundant wetness, and, usually, a difficulty about 

 heating. Nearest the ideal is a house contiguous to the labora- 

 tory, but in attachment to a range of educational houses, as in 

 the case of the one I am describing. There are descriptions 

 of other experiment houses mentioned by DETMER in his "Prac- 

 tical Plant Physiology," page 8, and there is a good description 

 of new physiological experiment houses at Bonn (Germany) 

 by Lloyd in the Journal of Applied Microscopy, 5, 1902, p. 1829. 

 There is also a valuable article upon greenhouse construction in 

 Bailey's " Cyclopedia of American Horticulture." 



The management of an experiment greenhouse, to keep 

 the plants therein under conditions for normal and healthy 

 growth, requires care, and some one person should be respon- 

 sible for this. The greatest danger comes from excessive dry- 

 ness, especially on bright, warm days, when the house may ap- 

 proach the conditions of a desert. Then such simple devices 

 as pans of water on the pipes are ineffective, and the best remedy 

 is to copiously wet down the cement floor with hose at eight 

 or nine o'clock, and again at noon, unless, indeed, the pipes 

 are sunk below the floor, as earlier suggested. It is also a good 

 plan to have as many plants as possible in the experiment house, 

 and it is sometimes advantageous to surround the plant under 

 experiment by a wall of other plants, which devices help to keep 

 more natural conditions of moisture. It is also well to have 

 in this house a form of simple hygrometer adjusted to agree with 

 a similar one in an adjoining house filled with thriving plants; 

 then, if the two are kept approximately alike, the moisture con- 

 ditions will be about correct. Again, all fumes and vapors, 



