16 



PRELIMINARY STUDIES. 



3. Examine large Beans and Peas, some dry and some 

 that have been soaked over night. On the outside of the 

 testa, or seed coat, notice the scar hilum where the seed 

 was attached, and near it a small opening, the micropyle. 

 Use a magnifying glass to see the micropyle. Split the 

 seeds. Near the hilum, and lying between the two coty- 

 ledons, find a 

 miniature plant. 

 At one end of 

 this is the radi- 

 cle, a small 

 pointed organ. 

 Connected with 

 the radicle is a 

 delicate struc- 

 ture which a 

 good magnify- 

 ing glass w r ill 

 show to be com- 

 posed of mi- 

 nute beginnings 

 of leaves, the 

 plumule. Exam- 

 ine also for these 

 structures Peas 

 and Beans that 

 have been ger- 

 minating from 



one to five days. How are the radicle and plumule located 

 in the seeds with reference to the hilum and micropyle ? 

 The use of the micropyle will be considered later. 



4. The cotyledons and the plumule and radicle with 

 the minute hypocotyl constitute the embryo. In the Bean 

 and the Pea, the stores of food that are to serve the plant 

 in the beginning of its growth, are in the cotyledons. 



FIG. 1. Section through a cotyledon of a Bean, 

 showing starch and aleurone granules in the cells. 

 Starch and aleurone are the nutrient materials 

 stored up for the future growth of the plant. 

 When the seed germinates, these substances are 

 converted into sugar, which is the form in which 

 the food passes from one part of the plant to an- 

 other. (X35.) 



