DICOTYLEDONS 



91 



207. 



Cotyledon 

 of a bean, showing 

 plumule. 



Sketch their 



the small round object between the halves at one end; can 

 you tell what it is ? 



Slip off the coat from a whole bean and 

 notice its texture. Hold it up to the light 

 and see if it shows any signs of veining. 

 See whether the scar at the hilum extends 

 through the kernel, or marks only the seed 

 coat. Does the coat seem to adhere to 

 the kernel more firmly at one point than 

 another ? If so, label this point chalaza. 

 Lay open the two flat bodies into which the 

 kernel divides when stripped of its coats, 

 inner face and label them cotyledons. Be careful not to 

 break or displace the tiny bud packed away between the 

 cotyledons, just above the hilum. Label the round, stem- 

 like portion of this bud, hypocotyl, and the upper, more 

 expanded part, plumule. Which way does the base of the 

 hypocotyl point, toward the micropyle, or away from it .' 

 Pick out this budlike body entire and sketch as it appears 

 under the lens. Open the plumule with a pin and exam- 

 ine it with a lens ; of what does it appear to consist.' Do 

 you find any endosperm around the cotyledons as in the 

 corn and oats } Break one of the soaked cotyledons, 

 apply some iodine to it, and report whether it contains 

 any starch. Where is the nourishment for the young plant 

 stored .' What part of the bean gives it its value as food .'' 



Notice that in the bean the embryo consists of three 

 parts, the hypocotyl, plumule, and cotyledons, which com- 

 pletely fill the seed coats, leaving 

 no place for endosperm. 



208. — Cotton seed with lint. 



122. Dissection of a Cotton 

 Seed. — (Where cotton can not 

 be obtained, morning-glory, 

 okra, or maple may be used.) 

 Scrape the lint from a seed of cotton as closely as pos- 

 sible, or if practicable, get a specimen of one of the smooth 

 seeded varieties in cultivation, and look for a faint line or 



