CHAPTER XXVII. 



FERNS CONCLUDED. 



THE SEXUAL STAGE OF FERNS. 



270. THIS CHAPTER is LARGELY FOR READING AND FOR REFER- 

 ENCE, though the teacher should endeavor to give demonstra- 

 tions of the sexual organs, in their position on the under side 

 of the prothallium, and also sections to show the structure. 

 Prepared slides may be purchased for the purpose if it is not 

 possible to obtain the material for making them. Prothallia 

 may be grown by sowing the spores of ferns collected during the 

 summer and saved in paper bags. If possible, a gardener in a 

 greenhouse where ferns are grown should be consulted. Where 

 they cannot be grown, it may be possible to purchase the pro- 

 thallia also for study. When these can be obtained the student 

 should make as careful an examination of the prothallium as 

 possible before they are examined under the microscope. 



Exercise 54. 



271. Prothallium. Note the small size of the prothallium, its form, 

 color, delicate texture. Upon the under side observe the rhizoids. At 

 which end of the prothallium are the rhizoids attached ? With the aid of a 

 hand lens can you see any other projections from the under side of the pro- 

 thallium ? Where are they located? Sketch a prothallium showing the 

 under side and all the parts that can be seen with the aid of a hand lens. 



Demonstration 39. 



272. To show the sexual organs attached to the under surface of the 

 prothallium. Mount a prothallium with the under side uppermost in water 

 on a glass slip, and prepare for examination with the microscope. Study 

 with the low power of the microscope. Near the sinus of the heart-shaped 



166 



