MONOCOTYLEDONS AND POLYCOTYLEDONS 



89 



202 203 



202, 203. — Pitch 

 pine seeds (Gray) ; 

 201, scale, or open 

 carpel, with one seed 

 in place ; 203, winged 

 seed, removed. 



like a samara of the maple, but it differs from all forms 



of the achene in being' a true seed and not a fruit. Notice 



that the pine has no closed seed vessel, 



or ovary, like the other specimens we 



have been considering, but bears its seed 



naked in the axil of the cone scales, 



which may be considered open carpels. 



Hence, plants of this kind are called 



Gyviiiosperms, a word that means "naked 



seeds." 



Look at the bottom, or little end of 

 the seed, with your lens, for a small 

 opening like a pin hole. Make an en- 

 larged drawing of the seed as it appears under the lens, 

 labeling this hole micropyle, a Greek word meaning " a 

 little gate," because it is the entrance to 

 the interior of the seed. 



'Remove the coat from a seed that has 

 been soaked for twenty-four hours, and 

 examine it with a lens. Pick out the 

 embryo from the endosperm. Does the 

 endosperm resemble that of the corn 

 arfd wheat t Test it with iodine for 

 starch. How does the embryo differ 

 from those already examined .' How many cotyledons 

 are there ? 



Plants having more than two seed leaves are said to be 

 polycotyledonous, a word meaning "having many cotyle- 

 dons." This structure is characteristic of the pines, firs, 

 hemlocks, and some other plants, mostly belonging to the 

 Gymnosperms, or naked-seeded class. 



204. — Section of pine 

 seed, showing the poly- 

 cotyledonous ennb(-yo 

 (Gray). 



PRACTICAL QUESTIONS 



1. What gives to Indian corn its value as food? To oats ; wheat; 

 barley; rye; rice? (118, 119.) 



2. Which of these grains have the larger proportion of starch or 

 other endosperm to the embryo? 



3. Do the husks or seed coats contain any nourishment? 



