68 



suaaEsrj(jj\^s j-yji laboratory wouk. 



It is difficult to make a satisfactory section of tlie ovule of the 

 Bean, but by making a large number of transverse sec- 

 tions of an ovary of a j'ouug flower of Marsh-Marigold 

 some good sections will be secured, which will show the 

 essential parts. Note the two coats of the ovule, each of 

 several layers of cells. Observe the micropyle, and 

 within the coats the nucellus. In the latter is a large 

 cell, the embryo-sac, which should be examined with 

 a high power, in order to observe the central nucleus, the 

 ovum with the two synergidae, near the micropylar end, 

 and the antipodal cells at tlie opposite end. 



Fertilization. The details of the process may be observed 

 in flowers of Marsh-Marigold, Evening-Primrose, Vero- 

 nica serpyllifolia, and others : sections made through 

 the stigma will show the pollen-tubes penetrating the 

 tissue, and an examination of the ovules will often show 

 the tubes entering the micropyle. 



The Seeds. As has been already pointed out the seed is 

 characterized by the presence of the embryo, which is 

 formed by cell-division in the embryo-sac, as a result of 

 fertilization. 



Seeds of Bean and grains of Maize should be soaked in water 

 for a day or so and sections made in both cases. Observe 

 the starch granules in sections of the cotj^ledon of the 

 Bean and of the endosperm of Maize. Are the granules 

 alike in l)oth cases ? Are there any other cell-contents ? 



