158 PROPAGATION OF PLANTS. 



artificial heat is required in winter, the pipes may pass 

 only under the two outside frames, and the center one 

 may be used for the plants after they have become well 

 rooted, or for other purposes. For convenience in reach- 

 ing the plants, and economy of space, the center stage or 

 frame is made double the width of the side frames, and 

 the depth of all depends upon the purposes for which 

 they are to be used. If for small cuttings only, then they 

 may be quite shallow not more than six to eight inches 

 deep ; but if grafting is to be done, then a greater depth 

 will be required, or from one to two feet in depth ; but 

 if the house is to be a kind of "general utility house" in 

 propagating plants, then the frames may be made of 

 various sizes and depths. The center frames may be 

 deep enough to hold potted stocks of good size, and the 

 side frames must be shallow, for growing small cuttings. 

 The pipes under the frames should be entirely shut in, 

 so that the greatest heat in the house will be under the 

 frames, in order to give what is termed "bottom heat" 

 to the cuttings, exciting root-growth in preference to 

 growth of the leaf and stems. There should be small 

 doors placed along the entire length, opening into the 

 passage-ways, that may be opened to let the heat escape 

 into the house when necessary to raise its temperature, 

 or to lower that under the frames. The passage-ways 

 between the beds should not be less than two and a half 

 feet wide, and three will be better. If the frames are 

 over four feet wide it will be inconvenient to reach across 

 them, and a house eighteen feet wide will allow of three 

 rows of frames, and two passage-ways of three feet each ; 

 or the outside frames may be three feet wide, and the 

 center one as it can be reached from both sides may 

 be six feet. 



Arrangements for ventilating the house may be made 

 to suit one's convenience or fancy, but the openings 

 should be mainly at the top or near the peak of the roof. 



