2. The outside of a broad bean.—Notice the flattened oval shape, with an indentation at one place (Fig. 1). What is the colour of the skin (seed-coat) of the bean seed? Is all the skin of this colour? A black scar extends along the edge from the indentation for about ¾ in. What is this scar? If beans in the pod can be obtained, see that the scar is the place of attachment of the seed stalk. Make drawings to scale, showing side and edge-views of the seed. Wipe the [Pg 2] bean dry and then squeeze it gently. Notice that a drop of water comes out at a point at one end of the stalk scar. There is evidently a little hole here. This little hole is called the micropyle. Mark its position by a dot on the drawing. 3. The inside of a broad bean.—With a sharp knife cut the seed-coat open, beginning at the side of the seed furthest from the micropyle, and carefully remove the seed-coat. Notice that near the micropyle the seed-coat forms a funnel-shaped depression, and that the point of the funnel is at the micropyle. Does anything fit into the funnel? A little cone may be seen to fill the funnel; this conical body is called the radicle. Make a drawing of the seed after the removal of the seed-coat. Look at the edge opposite the radicle and notice that a crack divides the body of the seed into halves. Put the point of your knife blade into the crack, and gently force the halves apart. They come apart without tearing, showing that they are naturally separate, although they fit so closely together. These two swollen bodies are called the cotyledons. Separate them and see, at the point where they join the radicle, a little curved rod, evidently a continuation of the radicle, lying between them. This rod is the plumule. Take off one cotyledon, and make a drawing of the inner face of the other cotyledon, with the adhering plumule and radicle (Fig. 2). 4. Starch present in the cotyledons of the bean.—Scrape the inner surface of a cotyledon and then pour on it a drop of iodine solution.[2] Is there any change? Pour also a drop of iodine solution on a piece of laundry-starch. Is a similar blue colour formed? What substance is probably present in the cotyledons of the bean? 5. The pea.—Examine a pea in a similar manner. Make drawings showing the stalk-scar, the micropyle, and the plumule and radicle with their manner of connection with the cotyledons. Does the end of the radicle point towards the micropyle? How many cotyledons has this seed? What shape and colour are they? Do they contain starch? [Pg 3] 6. The seed of the yellow lupine.—Compare this with the bean and the pea, and find out how many cotyledons it has, and whether they contain starch. Can you find the plumule? It is very small, but occupies a position similar to that of the plumule of the bean. Does the end of the radicle point to the micropyle?