SEEDS AND SEEDLINGS. 25 



amount of water into a narrow cylindrical glass jar. Cover the Peas 

 with a cork ; smear the edges of the cork so that it can slide inside 

 the jar, and pass a thermometer through a hole bored in its centre. 

 Weigh the cork down with lumps of lead or a number of weights 

 and mark its position by giimming a strip of paper on the outside of 

 the jar. Fit up a " control " experiment in which a cork with a ther- 

 mometer hangs into a jar containing some water but no seeds. Note 

 the rise of the cork as the Peas swell and push it up, and compare the 

 temperatures, at the beginning and end of the experiment, in the jar 

 containing the Peas and that containing water (or that of the sur- 

 rounding air). 



(d) Does imbibition cause rise of temperatiire in dead substances as 

 well as in seeds ? Put some powdered starch into a tumbler, to form a 

 layer about an inch deep, put an equal amount of water into another 

 tumbler, and set a thermometer into each. When the two temperatures 

 are equal, pour the water over the starch, stir with the thermometer, 

 and note the rise in temperature (how many degrees?). 



* (e) If a small wooden box (e.g. a cigar- box with the lid fastened 

 down by tacks) is filled with dried Peas and then immersed in water, it 

 will burst as the Peas absorb water and swell. Try this experiment. 

 A large mass of swelling Peas may lift a weight of more than 

 100 Ibs. 



(/) The force exerted by swelling seeds can also be shown by filling 

 an ordinary narrow-necked bottle with Peas, and placing it under 

 water in a basin ; the bottle should be left uncorked, and some rubber 

 bands should be put round it to prevent the shattered glass from being 

 thrown out. Another method is to fill with dry Peas an empty rabbit- 

 skull and let it lie in water ; the bones will be torn apart along the 

 seams (sutures) where they join each other. 



* (y) How is the absorption of water by seeds affected by temperature ? 

 Weigh about 30 grammes of dry Beans or Peas, place them in a beaker 

 of water at 35 C., set the beaker on a sand bath with a thermometer in 

 the water, and keep the temperature steady at 35 C. for two hours. 

 At the same time place an equal weight of seeds in cool water, with a 

 thermometer ; first let the water stand for a time till it acquires th 

 temperature of the room. At the end of two hours, wipe dry both lots 

 of seeds and compare the increase in weight in each case. The seeds 

 that have been kept in water at 3o C. will have absorbed from two to 

 three times as much as those kept in the cool water. 



* (h) Weigh about 30 grammes of dry Peas and place them in a 10 per 

 cent, solution of salt in a beaker or tumbler. At the same time put a 

 similar weight of Peas in distilled water (or tap water). Compare the 

 weights of the two lots of seeds alter two hours, wiping them dry 

 before weighing. Which lot has increased most in weight ? 



