Suggestions and Course of Study 141 



XI. On the Parts of Stems that Convey the Sap. 

 (a) Take a young plant, root and all (bean or shep- 

 herd's purse), put it into a bottle containing a weak 

 solution of eosin (red ink will do). Allow to stand 

 for three or four days. Observe: the root turns red, 

 the stem does not. Why? Are the veins of the 

 leaves colored ? (6) Make transverse and longitudinal 

 sections of the root and stem. Observe: what areas 

 are affected by the stain? the fibro vascular bundles? 

 It is through these, the'n, that the upward flow of sap 

 takes place. Would the sap be so apt to reach the 

 leaves if evaporation were not prevented by the cuticle 

 and bark on the stem? 



XII. On Respiration, (a) Immerse some water- 

 plants (chara, spirogyra) in a beaker or tumbler full 

 of water; place in sunlight. Observe: bubbles rising. 

 (&) Place a funnel over the plants under water, and 

 over the funnel invert a test-tube filled with water. 

 Observe the bubbles rising into the test-tube and dis- 

 placing the water. After some days, when the test- 

 tube is half emptied of water, the upper part of the 

 tube being occupied by the bubbles, light a long 

 splinter and after it has burned for some time blow it 

 out and insert the glowing point of the stick into the 

 test-tube. It bursts into a flame. This is evidence of 

 oxygen. The plant has been exhaling oxygen, (c) 

 Breathe through a glass tube or straw immersed in a 

 tumbler of water. Observe: bubbles rise as in the 

 case of the plant. Put into the tumbler clear lime- 

 water instead of fresh well-water. On breathing into 

 this, for some time it turns cloudy. Evidence of carbon 

 dioxide CO 2 . (d) Take two tumblers or beakers filled 

 with water; put into each the same kind and quantity 

 of water-plants. Place one in bright sunlight, the other 

 in shady place. In which are the most bubbles pro- 

 duced? What conclusion is to be drawn? 



Remarks: Plants, like animals, exhale carbon diox- 



