A MANUAL OF BOTANY 3 



starch with the weak iodine, and you see a deep blue purple 

 color, tlie characteristic reaction when iodine is added to 

 anything containing starch.) Such a large accumulation of 

 starch is called food storage. What is this food stored for ? 

 Name ten large seeds that have a similar storage. 



2. The Corn — A Monocotyledon 



Statement. Kernels of large yellow corn, soaked for 

 twenty-four hours, are to be preferred, although any kind of 

 field corn will answer. 



External features. A corn " seed " will be found to have 

 two broad faces, two narrower margins, a blunt and a coni- 

 cal end. Compare the faces and observe that one has an 

 oblong lighter area called the embryo, occupying the central 

 part of 1?his face near the conical end. 



Seed coat. With a sharp knife, determine whether or 

 not the corn has a seed coat similar to that found in the 

 bean. Break off the conical end and observe the dark 

 oblong scar concealed in the grain within this end. This is 

 called the funiculus. What purpose has this pointed end 

 and what structure had the same use in the bean ? 



Internal features. With a sharp knife make four sec- 

 tional cuts through the corn, viz. : (1) A cross section near 

 the blunt end and outside of the embryo. (2) A cross sec- 

 tion through the embryo, near the middle of the kernel. 

 (3) A long section midway between the two margins and 

 perpendicular to the embryo face. (4) A long section 

 parallel to the embryo face and about one-third of the dis- 

 tance through tlie seed from this face. 



Appearance with iodine. After examining each section 

 stain them with weak iodine and study the various parts 

 that now appear much more distinctly. The part unstained 

 in the different sections is the embryo, which may be seen 

 to consist of an outer scutellum or cotyledon and a central 



