322 



ELEMENTARY STUDIES IN BOTANY 



It will be necessary to leave the pan partly open now and then 

 to allow gas exchanges. The principles of this simple piece 

 of apparatus may be used with a variety of details ; as, for 

 example, the substitution of two soup plates, one used as a 

 cover, for the tin pan and the pane of glass (Fig. 4a) . Of course 

 the most complete test of the germinating power of seeds is 

 obtained by planting in soil in conditions they must meet 



when sown for a crop. It 

 should be known that seeds 

 usually germinate much bet- 

 ter in the ordinary germina- 

 tion tests than they do when 

 actually put in the ground 

 out of doors, so that one 

 must not expect that the 

 actual germination will 

 equal the experimental ger- 

 mination. 



The length of time neces- 

 sary for germination varies 

 widely with different seeds, 

 and these periods should be 

 learned for plants that one 

 cultivates. As a rule, the 

 period of germination is 

 somewhat longer in soil than in the ordinary testing experi- 

 ments in artificial conditions. As has been stated, some 

 seeds have such a hard and bony covering that germina- 

 tion may be very much delayed, and in nature such seeds 

 may lie for a season or two or even many seasons before 

 germination occurs. It is evident that any treatment of 

 seeds that will hasten germination is of advantage, but many 

 suggested treatments have been disapproved for most seeds, 

 as soaking in water or in certain chemicals before planting. 

 It has been found, however, that any mechanical method of 



FIG. 4a. A seed-germinator constructed 

 by using home utensils, as soup plates 

 or basins : in the upper figure the ger- 

 minator is closed ; in the lower figure 

 it is open, showing the sheets of moist 

 blotting paper (kept moist by water in 

 the plate) between which the seeds are 

 placed. After WESTGATE. 



