ONION 



21 



distance above this is a very narrow slit (s), through which the 

 first green leaf of the plumule makes its exit (s, s, Fig. 6). 

 After one leaf emerges others soon follow, the younger ones 

 coming out in regular order through slits in the sides of those 

 immediately older than themselves. 



Ex. 12. — Soak fresh onion seeds in water for a few hours. With a razor 

 cut through some parallel to their fiat sides in order to show the embryo 

 within, as at I, Fig. 6. 



Sow others in damp blotting-paper ; allow them to germinate and the 

 seedlings to develop ; make observations of them at different stages of growth. 



Watch the germination of seeds sown in boxes or pots containing ordinary 

 garden soil. 



Fig. 7- — I. Outline of wheat grain showing the position and form of the 

 embryo. 2. Longitudinal section through a wheat grain. 3. Wheat 

 grain germinating. 



Sc Scutellum ; p plumule ; r^ primary root ; r^ secondary root ; co 

 coleorhiza. 



13. Plants whose embryos possess only one cotyledon are 

 known as Monocotyledons, and form the second large class of 

 seed-bearing plants. 



Few of the representatives of this class with which we are 

 ordinarily familiar have true seeds large enough for examination. 

 The onion is probably one of the best commonly occurring 



