THE SPERMAPHYTES. 



239 



the flask with a rubber stopper having a bent tube. 

 Place the hands on the flask to warm it and drive out 

 some of the air, and then support it with the outer end 

 of the bent tube dipping under mercury. As the Barley 

 germinates, the carbon dioxide given off is absorbed by 

 the caustic potash solution. The oxygen of the air in 

 the flask is used by the plant, as is evidenced by the mer- 

 cury which rises to offset the tendency to form a vacuum 

 in the apparatus. 



18. Show that heat is produced by germinating seeds. 

 Fit two 500 c.c. flasks with stoppers bearing thermometers. 

 Fill one of the flasks one third full of 



Peas that have been soaked in water 

 twelve hours, letting the bulb of the 

 thermometer be well covered with 

 Peas. Note the reading of the two 

 thermometers. Set both flasks in 

 same conditions, and after some hours 

 take the readings of the thermometers 

 again. Has heat been produced by 

 the germinating seeds ? 



19. Study the food materials neces- 

 sary for the healthy growth of plants. 

 Germinate seeds of Peas, Beans, and 

 Buckwheat on clean sand until they 

 are well started. Transfer some to 

 pots of ordinary loam. Make cultures 

 of others as follows : Fit large test 



tubes or small cylinders with corks that have been split 

 vertically and the centers somewhat hollowed to allow 

 room for the seedling. Secure a seedling in each cork by 

 means of asbestos fiber so that its root will dip in the 

 solution to be placed in the cylinder. In one cylinder 

 place distilled water ; in another ordinary well or river 

 water ; in several others Sachs' solution for green plants, 



FIG. 164. Cylinder for 

 the cultivation of 

 seedlings in differ- 

 ent solutions. (After 

 Hansen.) 



