132 LABORATORY AND FIELD EXERCISES 



and compare them with those of ferns and 

 Selayinella. Do cycad spores differ in structure 

 or in function from those of Pteridophyta ? 

 (4) Drawings. Draw the ventral (abaxial) view of a 

 microsporophyll and its sporangia. Label. Draw 

 two or three microspores. . 



b. Megasporophylls and sporangia. 



(1) Eemove entire sporophylls with their megaspo- 



raiigia, or ovules, from the female strobili. Note 

 young or undeveloped megasporangia if found. 

 Are these megasporangia, or ovules, similar to 

 the ovules of the mandrake and the bean studied 

 earlier in the text ? Consult these earlier figures 

 and text descriptions. If they are the same, are 

 all ovules and seeds megasporangia ? 



(2) Gross structure of the megasporangium. Bisect the 



megasporangia of Zamia and study their structure 

 as shown on the cut surface. Compare the Zamia 

 megasporangium with that of the mandrake. Do 

 you find integuments, micropyle, and funiculus 

 in the megasporangium of Zamia ? What fills 

 the center of the sporangium ? Do you find 

 structures looking like archegonia, or eggs? Use 

 hand lens and examine your specimen carefully. 



c. Conclusions. What conclusions do you draw as to the 



nature of the megasporangium and its contents ? 

 Does it contain spores or structures belonging to a 

 gametophyte generation ? Does the sporangium ever 

 open (dehisce) as in the microsporangia ? State in 

 summary form your conclusions as to relation of 

 the megasporangia of Zamia to ovules of the man- 

 drake, locust, and bean studied in Part I, and to 

 megasporangia in the heterosporous Selaginella. 



