360 THE HIGHER DICOTYLEDONS. 



Plant tubers in the garden or in pots, some in moist saw- 

 dust, some in moist soil ; some in water, some in damp air in 

 covered vessels ; some with the bud end upwards, some with 

 this end downwards ; some cut in two, separating bud end 

 from stalk end, some cut into several pieces with an eye or 

 without an eye. After a week or two, when the buds begin 

 to sprout, it will be easy to tell the bud end from the stalk 

 end. Will the buds sprout if a tuber is kept in darkness ? 

 Do all the specimens gain in weight ? Which do not ? In 

 the case of specimens that gain in weight, where does the 



Fig. 148. Cells of Potato, showing Starch Grains, greatly magnified. 



extra material come from ? In the case of specimens grown 

 in darkness, at what stage do they die? In what other 

 respects do specimens ' grown in darkness differ from those 

 grown in the light ? Why do tubers with sprouting buds 

 turn soft? Chop up some sprouted tubers, shake up the 

 pieces in water ; then filter, and test the filtrate for (1) 

 starch, (2) sugar. 



In examining plants grown from tubers, note that the new 

 tubers are simply the swollen ends of branches, which can be 



