BIOLOGY OF HIGHER SEED PLANTS 



67, 



-str 



tulip, Narcissus, or Easter lily. Observe them care- 

 fully under low and high powers of the microscope. 



(1) Does the pollen cell have one or more nuclei? Do 



different pollen cells differ in this respect ? Do you 

 see granu- 

 lar cytoplasm 

 surrounding 

 the nucleus 

 in some pol- 

 len cells ? 



(2) Draw a pollen 



cell much en- 

 larged. Indi- 

 cate the gran- 

 ular condition 

 (Fig. 85, a) of 

 the cytoplasm 

 and the rel- 

 ative size of 

 the nucleus, 

 or nuclei, in 

 the cell. La- 

 bel your fig- 

 ure correctly. 

 (.">) Xtmly of pollen 

 tubes. If pol- 

 len tubes are 



available, study the structure and method of 

 formation of pollen tubes. Draw a pollen cell 

 and its pollen tube. Note and draw the structure 

 of the tube and its cytoplasmic contents. If pos- 

 sible observe the nuclei in the pollen tube. This 

 point is difficult to determine. 



- - - ou int 



FIG. 19. Diagram of the ovule, embryo 



sac, and embryo of shepherd' s-purse 



(Capselkt) 



ou int, outer integument ; in int, inner in- 

 tegument ; susp c, suspensor cells ; e s w, 

 embryo-sac wall ; r r, root region ; st r, stem 

 region ; s I, seed leaves. From Bergen and 

 Caldwell's "Practical Botany " 



