STORAGE OF NOURISHMENT IN THE SEED. 



21 



Compare the kernel of corn and its germination with the oat, Fig. 9. 



28. Experiment 9. Of how much Use to the Corn Seedling is the 

 Endosperm ? — Sprout kernels of corn on blotting-paper. When they get 

 fairly started, cut away the endosperm carefully from several of the seeds. 

 Suspend on mosquito netting over water in the same jar two or three 

 seedlings which have lost their endosperm, and as many which have not 

 been mutilated. Let them grow for some weeks, 

 and note results. 



29. Starch. — Most common seeds con- 

 tain starch. Every one knows something 

 about the appearance of ordinary commer- 

 cial starch as used in the laundry, and as 

 sold for food in packages of corn-starch. 

 It is not always easy, however, to recog- 

 nize at sight the presence 

 of starch as it occurs in 

 seeds, but it may be detected 

 by a very simple chemical 

 test, namely, the addition 

 of a solution of iodine.^ 



30. Experiment 10. 



Test Seeds with Iodine for 

 Starch.^ — Pulverize one or two 

 seeds,^ add two or three drops of 

 boiling water to soften and swell 

 the starch, and then add, drop 

 by drop, the iodine solution. 

 Only a little is necessary ; some- 

 times the first drop is enough. 



If starch is present, a blue 

 color (sometimes almost black) will appear. If no color is obtained in 

 this way, boil the pulverized seeds for a moment in a few drops of water, 

 and try again. 



1 The tincture of Iodine sold at the drug-stores wiU do, hut the solution prepared 

 as directed in Appendix B answers better. This may be made up in quantity, and 

 issued to the pupil in drachm vials, to he taken home and used there, if the ex- 

 perimenting must be done outside of the laboratory or the schoolroom. 



2 May be a home experiment. 



' With large seeds, Ulse a nut, only part of one will be necessary. 



Fig. 9. —The Oat. I, Fruit, longitudinal sec- 

 tion, li, canlicle ; G, plumule ; C, cotyle- 

 don ; A, endosperm ; T, testa ; O, wall of 

 ovary. II, Germination. G, plumule ; C, 

 cotyledon; Col, sheath of caulicle ; E, root. 



