and Laboratory Methods 



2621 



SERIES III. SPERMATOPHYTA. Sub-kingdom, GYMNOSPERMAE. 



LXXI. Cycas revoluta L. Cycad. 



Class and order, Cycadales. Family, Cycadaceae. 



This plant is usually grown in greenhouses and conservatories. Herbarium 

 and museum material should also be at hand. 



1. Examine a living plant and describe its general characters. Sketch the 

 stem, showing the scale leaves and one foliage leaf. 



2. Draw a megasporophyll (Carpel) from herbarium specimens, showing 

 the megasporangia or ovules. Note the similarity of the carpel to the foliage 

 leaves. The carpels are produced in a whorl like the foliage leaves, and the 

 stem continues to grow through the whorl. Compare this condition with the 

 ordinary ferns and with Lycopodiiun lucidiihnn. 



Fig. 12. — Diagram of life cycle of Selaginella. 



3. Make a sketch of the large staminate (microsporangiate) cone. Draw a 

 single microsporophyll (stamen), showing the numerous microsporangia (pollen- 

 sacs) on the under side. 



4. From alcoholic material draw a young ovule, properly dissected, showing 

 the integument with micropyle, the inner wall of the ovule (megasporangial wall) 

 with the pollen chamber, and the female gametophyte. 



5. Draw half of a large female gametophyte from a mature seed, showing 

 the little depression at the outer end and the dormant sporophyte embryo. The 

 necks of the archegonia open into this depression (called the archegonial cham- 

 ber) at the time of fertilization. 



6. Mount male gametophytes (pollen-grains) and draw under high power. 



7. If prepared slides are available study sections of pollen-grains showing 

 the internal structure. 



8. Note. — The fundamental difference between the heterosporous pterido- 



