344 THE BIOLOGY OF THE PLANT 



tense and stretched, *'. e., turgid ? "What changes 

 would take place in a tissue composed of such 

 cells 8 



h. Germination. 



Sow some beans, corn, and pumpkin seeds in 

 damp sawdust or sand, and put some flax and 

 mustard seeds on damp blotting-paper under a 

 bell-jar. Examine from day to day, and note the 

 changes which take place. "What is the first visi- 

 ble sign that germination has begun ? On which 

 day does the radicle appear? On which the co- 

 tyledons and caulicle ? "What becomes of the 

 seed-coats ? Note the behavior of the cotyledons 

 — how they are withdrawn from the seed-coats 

 and from the soil, how they expand or unfold, 

 and the changes which take place in the shape, 

 size, and color of the cotyledons as growth goes 

 on. "When do the first true leaves unfold ? "When 

 does the second pair appear ? In which direction 

 does the primary root grow ? Examine the roots 

 for root-hairs. Where do they first appear ? Do 

 they grow at the extreme tip of the root ? Ex- 

 amine with a microscope the hairs on a root 

 which is two or three inches long. How do the 

 hairs on the lower differ from those on the upper 

 end ? How do you explain the difl'erence ? Sow 

 some mustard seeds in loose, damp sand. After 

 they have germinated, carefully draw them out 

 of the sand along with the particles attached to 

 the root-hairs. Wash gently in water to get rid 

 of the unattached particles. Do you find that 

 much of the sand adheres to the root -hairs? 

 What do you consider to be the function of these 



