EXERCISE 62 



WHAT IS THE EFFECT OF DIFFERENT TEMPERATURES 

 ON GERMINATION? 



Materials. Pea seeds ; filter or blotting paper ; dishes with 

 covers. 



Directions for work. Soak all the seeds for twenty-four hours. 

 Divide the seeds into four or five lots and place each lot on 

 wet filter paper or blotting paper in a covered dish. Do not 

 use more seeds than will lie on the bottom of the dish without 

 crowding. Put one of the dishes in the coolest place available 

 but not where the seeds will freeze. Put another dish in the 

 warmest place available but not where the temperature will 

 rise to the boiling point. For the other dishes select places at 

 intermediate temperatures. It is desirable that the temperatures 

 at the various situations be as constant as possible, and the 

 average at each place should be obtained with a thermometer. 

 However, if it is not possible to secure uniform temperatures, 

 the results will be instructive, though not so exact. If it is 

 found that there is considerable variation of temperature, it 

 may be better to plant all of the seeds in sand or sawdust, 

 since the temperature in these substances will vary less than 

 in the air. A thermometer inserted in the soil among the seeds 

 will give the temperature, and readings may be taken several 

 times each day. 



If the seeds are placed in dishes it will be well to darken 

 them, since no doubt at least some of the seeds will be placed 

 in a dark place and the results will be fairly comparable only 

 if all are equally darkened. 



At the end of four or five days examine each lot of seeds and 

 note how many are sprouted, how many have not germinated, 

 the relative length of the sprouts, and the general appearance 

 of the seedlings. Record the observations in the table on page 78 

 and write a full description of your experiment, giving all 

 details that might in any way affect the results. What are 

 your conclusions about the effect of different temperatures 

 within the range of temperatures used? 



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