ZAMIA FLORID ANA 173 



5. With a hand lens observe the wall of the arche- 

 gonium, and within, filling the venter, the large 

 ovum, or egg. 



6. As outlined above (/, 1-4), examine and describe 

 an ovule one month older (about May i), carefully 

 noting the changes which the different parts have 

 undergone. Observe especially the development 

 of the hard inner layer of the integument. May 

 this feature be of any advantage to the plant? 

 If so, how? Does any of the nucellus remain? 

 If so, describe. Note, in the depression of the endo- 

 sperm, the openings into the archegonia. How many 

 are there? Draw this depression as seen in end 

 view. 



7. Construct a diagram of an ovule of this age as seen 

 in median longitudinal section, carefully labeling 

 all parts. 



8. Make a diagrammatic drawing of a cross-section of 

 the same ovule passing through the venters of the 

 archegonia. 



9. In ovules one month older (about June i) the sac- 

 like proembryo may be seen, lining the walls of the 

 venter of the archegonium, and, growing from its 

 basal end into the tissue of the endosperm, the 

 prominent suspensor, at the free end of which the 

 embryo begins to develop. As the suspensor and 

 embryo increase in size, a cavity is formed in the 

 surrounding endosperm. This cavity results from 

 the digestion of the endosperm tissue, which goes 

 to nourish the growing embryo and suspensor. 

 Suggest how this digestion and subsequent nutri- 

 tion may be accomplished. 



10. Make a drawing of a median longitudinal section 

 of the ovule at this stage. 



