1 1 o MAIDEN-HAIR FERN. 



sori. Note the pinnules from which they are most 

 uniformly absent. 



Soak a pinnule in water for a few minutes and with the 

 needles turn back 



b. The flap which covers a sorus, the indusium. Notice 

 that it is a portion of the edge of the pinnule 

 reflexed and peculiarly modified. 



c. On the under side of the indusium, a mass of yel- 

 lowish spheroidal bodies, the sporangia. 



Scrape away most of the sporangia from the surface, and 

 notice 



d. The relation of the points of attachment of the 

 sporangia to the veins. Cut off and draw an indu- 

 sium showing this. 



5. The sporangia. Mount some of the separated sporan- 

 gia and examine by oblique light. Note 



a. Their shape. 



b. The short stalk by which they were attached. 



c. The ridge, slightly darker than the rest, extending 

 part way round the sporangium, the annulus. 



d. Burst a sporangium and note the contents, minute 

 powdery bodies, the spores. 



c. Study the manner of bursting and scattering the 

 spores. Tear a bit of an indusium from a dried 

 specimen previously soaked in water, retaining 

 only a few sporangia ; place it on a slip of glass 

 and allow it to dry, while watching the sporangia 

 through a lens, illuminating them from above. A 

 crack appears on the side where the annulus is 

 absent, which gapes more and more as the annulus 

 straightens and becomes recurved. After bending 

 backward a certain distance, by a sudden jerk 

 whereby the spores are scattered, the annulus 



