THE BEAN SEED 261 



seed coat protect the young bean embryo. Other mark- 

 ings on the outside of the bean are the micropyle 

 (mi'kro-pil: Greek, micro, small; pyle, gate), a small dol 

 at one end of the hilum, and the raphe (ra'fe: Greek, 

 raphe, a seam), a band or ridge which extends Lengthwi 

 around the bean from the top of the hilum tu the bottom. 



The small stem or hypocotol is the part of the bean 

 embryo that first escapes from the seed coat when tin- 

 young bean begins to grow. One end of this small stem 

 soon develops into a root which grows into the groin id. 

 and the other end develops into a stem which grows 

 above the ground and lifts the seed leaves into the light. 



The seed leaves or cotyledons are by far the largest 

 part of the bean, and their size is due to the great amount 

 of food stored in them. They are the parts of tin- bean 

 seed which are important to man and animals as food. 



The seed bud or plumule consists of two small Leaves. 

 The plumule is connected closely with the food stored in 

 the seed leaves, which is taken up by the young plant 

 and used in growing. 



LABORATORY STUDY 



Place a few beans in dry sand in a warm room. Why do not the 

 beans grow and sprout? Place others in water in a warm room. What 

 happens ? Place other beans in moist earth (a) in a warm room ; M in 

 a cool place. Examine in a few days. These several experiments show 

 the influence of temperatures, soil, and moisture on the sprout in g of beana 

 Heat a few beans in an oven for ten minutes and then place them in a 

 warm, moist soil. Why do they not grow? Soak beans for several 

 hours. Remove the testa and place them beside dry beans for a to- 

 days. What happens ? This experiment illustrates one use <<t the testa. 

 Examine a dry bean. Split it along the bark and observe I) the two 

 parts into which it divides. These are the cotyledons of the new plant. 

 Note (2) the pair of small white leaves which are the plumule <>t the new 

 plant; (3) the hypocotyl, below the cotyledons, from which the stem 

 and roots will grow; (4) the hard covering or testa. Look for the 

 micropyle and raphe on a bean not split. 



