LABORATORY EXERCISES 9 



THE LIFE HISTORY OF A PLANT 

 VI. THE SEED 



22. A dicotyledonous seed (Phaseolus). 



a. Draw two views of a bean seed to show the general form, the 



hilum, the micropyle and the chalaza. 

 h. From a seed that has been soaked in water remove the seed 



coats (testa and tegmen). Study the coats. 



c. Draw the embryo, showing the cotyledon and caulicle. 



d. Separate the cotyledons and draw to show the cotyledons, the 

 plumule and the caulicle. 



23. Other dicotyledonous seeds: 



a. Study a seed of Pisum as in 22a, h, c, and d. 



b. Compare seeds of Trifolium and Raphanus (or Brassica) with 

 those of Phaseolus and Pisum. 



c. Study a seed of Cucurbita as in 22a, b, c, and d. 



24. A monocotyledonous seed (Zea Mays). 



a. Draw that side of a grain of corn which shows the embryo. 



b. Remove the seed coats from a specimen which has been softened 

 in water and find the embryo embedded in the mealy endo- 

 sperm. Study the seed coats, but do not try to homologize 

 with those of the bean. They are more complex. 



c. With a sliding cut make a longitudinal section of a seed through 

 the shorter diameter so as to exactly halve the embryo. Draw 

 the section and identify cotyledon, plumule and caulicle. 



d. Cut another transversely at three points, so as to divide the 

 embryo into quarters. Draw the three sections. 



e. Compare a seed of Triticum with that of Zea. 



25. A seed of a Gymnosperm (Pinus). Study a pine nut noting the 

 character of the seed coat, endosperm and embryo. 



VII. Development of the Seedling 



26. Where in a germinating bean does evidence of growth first appear? 

 Where and how does the developing part first emerge from the 

 seed coats? Compare plumule and caulicle with regard to rate of 

 development during the first week of growth. 



27. Compare pea, squash and corn with bean in regard to each point 

 mentioned in 26. 



28. How does each of the four kinds of seedlings emerge from the soil? 



