34 PLANT PHYSIOLOGY 



standing), have tops of solid slate, 2X4 feet by i| inches thick, 

 resting on 4 adjustable nuts, and have a very solid cast-iron stand 

 of the form shown by figure 4 (the end view being somewhat 

 similar, though narrower, and with a vertical central piece).* 

 Of the very greatest importance is a physiological dark room, 

 in which plants may be kept in complete darkness, but under 

 good ventilation. Its plan is shown by figures 2 and 3. It 

 is wholly inside the greenhouse, whose average temperature it 

 takes and keeps very constantly. It is built of one thickness 

 of brick (3! inches), and has an entrance-way, made of matched 

 boards, so arranged that by opening one door at a time it is pos- 

 sible to enter and leave the room without admitting any light. 

 The doors fit tightly into angled cases, and are further made 

 light-tight by rubber weather strips. The alternate bricks, one 

 row above the floor all around (except at the entrance), are 

 omitted, and over the openings is built the arrangement of boards 

 wholly painted black, shown in' section by figure 3; this freely 

 admits air, but no light. The same end is accomplished in the 

 roof by the triple arrangement shown in section in figure 3. 

 This roof is black throughout except on the top, where it is 

 painted white to reflect as much heat and light as possible. 

 Shelves at convenient heights are added (the lower ventilation 

 box serving as one set), and an incandescent electric light per- 

 mits the room to be lighted when desired. In use it has proven 

 wholly satisfactory. 



Another very important furnishing is a large sink. In the 

 greenhouse I am describing this is placed against the labora- 

 tory wall in the position of the hood shown by figure 3, but I 

 can suggest a much better place for it, as noted below. I have 

 discovered one, and only one, marked defect in this green- 

 house and laboratory equipment, viz., it has no suitable, but 

 only a small makeshift, place where heating can be done in such 



♦These tables were designed, and other good features of the houses were sug- 

 gested, by Mr. W. A. Burnham (of the firm of Lord and Buknham, New York, 

 builders of the houses), who took a deep and generous interest in the develop- 

 ment of these houses as an educational equipment. 



