20 Elementary Work in Botany. 



bean is two inches long a whorl of spreading rootlets ap- 

 pear as shown in the figure on this page. 

 Let ns see how they act when the caulicle 

 grows. Suppose the hypocotyl lengthens 

 and the part below the bend remains 

 straight, what will be the result ? Is it 

 not plain that if the rootlets were re- 

 moved the result would be quite differ- 

 ent? In some of your embryos the 

 Fig. is. sprouting sun- hypocotyl does not grow. How do such 



flower seed, showing side -, ->-TTTI . -11 



rootlets beiow the hypo- seeds come up ; W ork upon this problem 

 of how seeds come up until you have 

 acquired a thorough understanding of it.* 



EXERCISE 12. 



Study your sprouting corn and wheat. If the sprouts 

 are half an inch long, or longer, taste of the endosperm and 

 the embryo. What do you think part of the starch has been 

 changed into? Has this substance been formed in all your 

 growing seeds? Which sprout appears first, the caulicle 

 or the plumule ? Does more than one sprout come from the 

 caulicle end of the embryo ? 



Examine all your seedlings. In which have the coty- 

 ledons grown? If the cotyledons do not grow, does the 



* Since circumnutation of the caulicle only facilitates its movement through the 

 ground, and has nothing to do in determining which end shall move, it need not 

 be considered here. The experiments which will enable one to see that all 

 growing stems circumnutate are not easy enough for beginners. [See Darwin'8 

 " Movements of Plants."] 



