THE SEED 



13 



portion, endosperm, the depression near the center, embryo, or 

 germ. 



Next take a grain that has been soaked for twenty-four 

 hours. \Vhat changes do you see ? How do you account for 

 the swelling of the embryo? Remove the skin and observe 

 its texture. Make an enlarged sketch of a grain on the 

 grooved side with the coat removed, labeling the fiat oval body 

 embedded in the endosperm, cotyledon ; the upper end of the 

 little budlike body embedded in the cotyledon, plumule, the 

 lower part, hypocotyl— words 

 meaning, respectively, " seed 

 leaf," "little bud," and 

 " the part under the cotyle- 

 don." As this part has not 

 yet differentiated into root 

 and stem, we cannot call it 

 by either of these names. 

 The cotyledon, hypocotyl, 

 and plumule together com- 

 pose the embryo. Pick out 

 the embryo and sketch as 

 it appears under the lens. 

 Crush it on a piece of white paper; what does it contain? 



Make a vertical section of another soaked grain at right 

 angles to its broader face, and sketch, labeling the parts as 

 they appear in profile. Make a cross section through the 

 middle of another grain and sketch, labeling the parts as be- 

 fore. What proportion of the grain is endosperm and what 

 embryo ? Put a drop of iodine and of nitric acid separately 

 on pieces of the endosperm, and note the effects. Test the 

 seed coats and the cotyledon to see if they contain any starch. 



Notice that the corn grain has but one cotyledon, hence 

 such seeds are said to be monocotyledonous, or one-cotyledoned. 

 The grains are not typical seeds, but are selected for examina- 

 tion because they are large and easy to handle, can be ob- 

 tained everywhere, and germinate readily. 



14 15 10 



Figs. 14-16. — Dissection of a grain of 

 corn : 14, soaked grain, seen flatwise, cut 

 away a little and slightly enlarged, so as to 

 show the embryo lying in the endosperm ; 

 15, in profile section, dividing the grain 

 through the embryo and cotyledon ; 16, the 

 embryo taken out whole. The thick mass is 

 the cotyledon ; the narrow body projecting 

 upwards, the plumule ; the short proje? ion 

 at the base, the hypocotyl {after Gray). 



