18 PRACTICAL COURSE IN BOTANY 



remove the hard coat, or testa, as it is called. The thin, green- 

 ish covering that lines it on the inside is the endosperm. How 

 does it compare in quantity with that in the corn and castor 

 bean? How do the cotyledons compare in thickness with 

 those of the bean? Carefully separate them and draw, label- 

 ing the parts as you make them out. The tiny pointed 

 object between the cotyledons at their point of union is the 

 plumule ; is it as well developed as in the bean ? Can you see 

 any reason why seeds like the pea and bean, which have coty- 

 ledons too thick and clumsy to do well the work of true leaves, 

 should have a well-developed plumule, while those with thin 

 cotyledons, like the squash and pumpkin, do not, as a general 

 thing, form a large plumule in the embryo ? The little pro- 

 jection in which the cotyledons end is the hypocotyl; which 

 way does it point ? Where did you find the micropyle to be ? 

 Test the cotyledons and some of the endosperm for food sub- 

 stances ; what do you find in them ? 



15. Study of a pine seed. Remove one of the scales from 

 a pine cone and sketch the seed as it lies in place on the cone 

 scale. Notice its point of attachment to 

 the scale, and look near this point for a 

 small opening, which you can easily recog- 

 nize as the micropyle. The seed with its 

 wing looks very much like a fruit of the 

 maple, but differs from it in being a naked 

 27 28. see( j borne on the inner side of a cone scale, 



FIGS. 27, 28. 



Pitch pine seeds: without a pod or husk or outer covering of 

 27, scale or open an y \^A suc h as beans and nuts and grains 



carpel, with one seed . . 



in place ; 28, winged are provided with. Plants like the pine, 



ged, removed. (After 



Gymnosperms, a word that means " naked 

 seeds/' in contradistinction to the Angiosperms, which bear 

 their seeds in pods or other closed envelopes. 



Remove the coat from a seed that has been soaked for 

 twenty-four hours, and examine it with a lens. Does it con- 

 sist of one or more layers? Is there any difference in color 



