242 ELEMENTS OF SYLVICULTUKE . 



rows of frames, and frames in each row. The sieves 

 are capable of sliding horizontally in grooves, and are 

 furnished below with rollers to facilitate this motion. 

 Thermometers suspended inside constantly permit 

 of the regularisation of the temperature. 



It is very easy to understand the working of the 

 apparatus. The sieves are filled with cones, and all 

 the little doors closed. The stove is heated, gene- 

 rally with empty cones. The hot air fills the room, 

 and as it is constantly renewed, it descends after 

 striking the roof, and escapes by the chimneys carry- 

 ing the watery vapour along with it. The draught 

 is increased or lessened at pleasure by widening or 

 narrowing the mouth of the chimneys. The scales 

 gradually open. From time to time each little door 

 is opened, and the cones are shaken about by pulling 

 the frames to and fro ; and the seeds fall eventually 

 into the lowest row of frames. When the cones are 

 quite open, they are taken out and replaced by fresh 

 ones ; thus the process is continuous. The tempera- 

 ture of the close room is regulated by means of the 

 thermometers, as it is essential not to exceed a cer- 

 tain degree of heat, otherwise the vitality of the 

 seeds would be destroyed. For pines and the spruce 

 fir, the temperature maybe allowed to rise as high as 

 40 Centigrade ; for larch the temperature is lower, 

 and should be increased only gradually; otherwise the 

 resin in the cones would melt and glue the scales 

 together, thus preventing the seeds from falling out. 

 If, on taking out the cones from the close room, 

 it is found that the lower scales are not properly 

 open, which is nearly always the case, the remain- 



