48 



SEEDS AND SEEDLINGS. 



iodine solution, which gives only a brown stain ; there is no 

 starch, but proteids and oil are present (Fig. 25). 



Fig. 25. Sunflower. A, akene ("seed ") ; B, same with half of the shell removed ; 

 C, enrbryo with one cotyledon removed ; D to H, stages in germination. 



80. Maize and Wheat. G-et Maize grains, also a Maize 

 " cob," from a corn merchant ; the White Horsetooth variety 

 is best, being larger and more regular in form, for examining 

 the structure of the grain. If possible, examine a young cob, 

 noting the long feathery stigma which falls off from the broad 

 free end of the grain as it ripens. In the grain, note the oval 

 patch on one side, showing two marks (sometimes furrows and 

 sometimes ridges) in a straight line, one towards the top (broad 

 end) and one towards the bottom of the patch. 



Peel off the thin tough skin and with a needle raise the 

 plumule and radicle which cause the two marks already 

 noted ; lay a grain on the table and make a clean slice 

 through the middle of the patch if this is carefully done you 

 will see the plumule and radicle, attached to a thick body 

 which projects into the grain (Fig. 26, C) ; smear the cut 

 surface with iodine solution, which stains the young plant 

 (radicle, plumule, and single cotyledon) brown, and the rest 

 of the grain dark blue if the grain has been soaking in 

 water for a few days, some starch will be present in the 

 embryo, because part of the starch stored in the other part 

 of the grain has been changed into sugar by diastase, trans- 

 ferred to the embryo, and there re-converted into starch. 



