IV. SEEDS AND SEEDLINGS 



MONOCOTYLEDONS AND POLYCOTYLEDONS 



Material — Dry and soaked grains of corn and oats, or other 

 grasses. Seed of pine; tlie cones should be gathered in September 

 or October, and kept until needed. 



118. Dissection of a Grain of Corn. — Examine a dry grain 

 of corn on both faces. Sketch the grooved side, labeling 

 the hard, yellowish outer portion, endosperm, the depression 

 near the center, embryo, or germ. 



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

 to twenty-six hours. What changes do you see } How do 

 you account for the 

 swelling of the embryo \ 

 Remove the skin and 

 observe its texture. Is 

 it a pericarp, a seed 

 coat, or both.' (Sec. 91.) 

 Sketch the grain with 

 the coat removed, label- 

 ing the flat oval body 

 embedded in the endo- 

 sperm, cotyledon, the up- 

 per end of the little bud- 

 like body embedded in 

 the cotyledon, plumule, the lower part, hypocotyl — words 

 meaning respectively, " seed leaf," " little bud," and " the 

 part under the cotyledon." As this part has not yet dif- 

 ferentiated into root and stem, we can not call it by either 

 of these names. The cotyledon, the hypocotyl, and the 

 plumule together compose the embryo. Pick out the 

 embryo and sketch it as it appears under the lens, then 



87 



197-199. — Dissection of a. grain of corn 

 (Gray) : 197, soaked grain, seen flatwise, cut 

 a\vay a little and slightly enlarged, so as to 

 show the embryo lying in the endosperm ; 

 198, in profile section, dividing the grain 

 through the embryo and cotyledon ; 199, the 

 embryo taken out whole. The thick mass is 

 the cotyledon; the narrow body projecting 

 upwards, the plumule; the short projection at 

 the ba^e, the hypocotyl. 



