BIOLOGY OF HIGHER SEED PLANTS 27 



(1) The nucleus. What is the general nature of the 



nuclear protoplasm ? Does it appear granular or 

 homogeneous ? Compare the nuclear protoplasm 

 with the regular cell protoplasm or cytoplasm. 

 Can you detect a thin nuclear membrane, or wall, 

 around the nucleus, and a darker granule, the 

 nucleolus, within the nuclear cavity ? Is the 

 nucleus located in the center of the cell ? How 

 is it supported in this position ? 



(2) Vacuoles. What forms the bounding walls of the 



vacuoles ? What are they supposed to contain in 

 living cells ? What is the origin of vacuoles and 

 how do they grow ? Consult the text. 



(3) The cytoplasmic sac. What is the cytoplasmic sac 



and how formed ? What relation does the cyto- 

 plasmic sac bear to the general protoplasm of the 

 cell ? to the central vacuoles and to the cell wall ? 



(4) Draw two cells greatly magnified (one inch in diam- 



eter) to illustrate two stages in the formation of 

 vacuoles. Put details of the nucleus and cytoplasm 

 in each cell. 



CELL STRUCTURE AND PROTOPLASMIC STREAMING IN 

 STAMEN HAIRS OF TRADESCANTIA (SPIDERWORT) 



1. Mount some of the delicate, haiiiike outgrowths (stamen 



hairs) which grow out from the stamens in flowers of 

 Tradescantia, the common spiderwort. Preserved ma- 

 terial may be used for the cellular structure of the 

 stamen hair. 



2. Low-power study. What is the general cellular structure 



of a stamen hair ? , How do the cells composing it differ 

 in size and form at the smaller apex and at the larger 



