18 Elementary Work in Botany. 



your unplanted growing seeds. Notice particularly those 

 which have rootlets growing from the side of the caulicle. 

 Which of these have developed hypocotyls ? In which 

 have the epicotyls grown most ? What changes have taken 

 place in the cotyledons? Make drawings showing the 

 present condition of the bean and scarlet runner in your 

 jar. The India-ink dots should show what portions of the 

 caulicles have grown most since you marked them. Which 

 one is like the Windsor bean in its growth ? In which has 

 the epicotyl grown most ? 



It is important that you find out whether rootlets appear 

 before or after the hypocotyl begins to grow; and in em- 

 bryos which do not produce a noticeable hypocotyl you 

 must note whether the growth of the epicotyl begins before 

 or after the rootlets start. You must make your seeds tell 

 you all about the relation between the growth of rootlets, 

 hypocotyl, and epicotyl, for without this knowledge you 

 cannot understand how seeds "come up." This first work 

 of a plant in its second season's growth is not so simple as 

 is commonly supposed; and to understand how it is done 

 will try your skill in observing and thinking.* 



EXERCISE 11. 



Suppose a bean planted in sand to have grown a sprout 

 one inch long, as shown in the figure on page 19. Evi- 

 dently the sand around it must have been pushed out of the 



* A plant is called an embryo during its first season's growth. This growth 

 is nourished by the mother plant. [See note, p. 2.] 



