16 



EXPERIMENTS WITH PLANTS 



carried on by weighing in the same way as in the 

 previous one, and will afford interesting results for 

 comparison. 



What seed-covers admit water most readily? We 

 may make a satisfactory test by splitting the covers 

 of dry seeds in halves, removing the germ and allow- 



20. Seed-covers Hoating on water, each containing a few sugar crystals, 

 whicli, by dissolving, indicate the rapidity of osmosis; controls 

 on the glass strip. 



ing the dry covers to float like boats on the surface 

 of the water (see Fig. 20). Into each put a few crys- 

 tals of sugar, the dissolving of which will indicate 

 how rapidly water is absorbed through the cover. On 

 a dry piece of glass, near the surface of the water 

 but not in contact with it, place other boats contain- 

 ing sugar crystals, to see whether the sugar can absorb 

 enough moisture from the air (or from the cover) to 

 dissolve. In making the boats, we must take care 



