SEEDLINGS II3 



watch it from day to day. In what part does growth take 

 place ? Mark off a node of the stem in a similar manner 

 and find out how it grows. Allow a seedling to develop 

 until it has put forth several leaves, and measure daily the 

 successive internodes. Does an internode stop growing 

 when the one next above it has formed .■■ When is growth 

 most rapid .' Reverse the position of a number of seed- 

 lings that have just begun to sprout and watch what will 

 happen. A good way to observe the growth of roots is to 

 fill a glass jar or a lamp chimney with moist cotton or saw- 

 dust, and insert the seedling between the side of the jar 

 and the moist filling. 



154. Cotton. — Examine a number of cotton seedlings 

 in different stages of growth. What part appears above 

 ground first ? How does this compare with the first ap- 

 pearance of the bean .■' Of corn and oats ? Pull up a seed- 

 ling that has just begun to sprout; does the root come 

 from the big or the little end of the seed ? Does this agree 

 with what you learned about the position of the hypocotyl 

 in Sections 121 and 122.' Notice how the coats adhere 

 at the chalaza, even after the cotyledons are well above 

 ground ; is this woolly nightcap of any special service to 

 a delicate plant like the cotton ? Notice the little speckled 

 glands that cover the stem and the cotyledons. What 

 change of color do the latter undergo as the seedling de- 

 velops .'' How do they compare as foliage leaves with 

 those of the bean, squash, etc. ? With the foliage leaves 

 of the mature cotton plant ? Of what use to a plant are 

 the cotyledons when they appear above ground.? To 

 answer this question cut away the cotyledons from a 

 number of seedlings as soon as they appear, and ob- 

 serve the result as compared with others that have not 

 been cut. 



Pull up a seedling and sketch it entire, showing the 

 long, straight taproot. How does it compare in length 

 with that of the bean ? How do both differ from those of 

 the corn and oats ? Measure the growth of the root and 



ANDREWS'S BOT. — 8 



