THE BROAD BEAN PLANT. 



13 



31. The Seed. Examine some pods containing seeds, 

 also get a supply of dry seeds (Windsor Broad Bean, about 

 6d. per quart). Notice the black (or brown) mark on the 

 thicker end of the seed (Fig. 5). How was this mark on 

 the loose seed produced ? How does the seed become loose, 

 and what does it break from when the pod opens ? This 

 mark may be called the scar of the seed-stalk. In what 

 respects do dry seeds differ from fresh seeds ? 



Fig. 5. Seed of Broad Bean. A, C, and H are views of the entire seed ; B, D, E, F, 

 and G are views of the embryo (seed-coat removed) ; J and K, seed cut across (in 

 J the cotyledons and radicle are removed, to show the radicle-pocket). 



Put the dry seeds into water, and notice that in a few days they 

 have swelled and become smooth and rounded, like the fresh seeds. 

 Fill a wooden box, at least a foot deep, with moist sawdust, bog moss, 

 or soil, and plant seeds about half an inch below the surface. See 

 Chapter II. for details of germination. In the young green shoot that 

 comes above the soil notice the forms of the earliest leaves. 



32. Seed-coat. Examine from time to time some dry seeds which 

 have been placed in water, and notice that at first the surface becomes 

 thrown into folds. Cut across the seed, and note that these folds are 

 produced by a coat which encloses the contents of the seed. Evidently 

 the coat at first absorbs water and swells more rapidly than the con- 

 tents ; this loosens the coat and makes it much easier to remove in a 

 seed that has been soaked in water for a day or two. The wrinkling 

 of the seed-coat is very marked in French Bean and Scarlet Runner. 



