FERNS. 115 



I. The leaf-stalk, stipe, with many thin, brown scales. 

 Are these persistent or deciduous ? 



II. The outline of the frond and the form of its main 

 divisions, pinnae. 



Ill* How the pinnae are divided. Compare the descrip- 

 tion of this species in Gray's Manual, p. 688. 



IV. The venation. Select one of the pinnae in which 

 this is well denned, and draw it carefully in outline, tak- 

 ing pains to represent accurately the exact position of the 

 veins, tracing them to the end of their ultimate divisions. 



Fructification. 



I. The conspicuous bodies on the under side of the 

 pinnae are the sori, or fruit-dots. Observe 



1. Their position. Are they situated on the back or 



alongside of the veinlet? 



2. The thin, scale-like covering, indusium, protecting 



the spores. 



II. Taking specimens nearly or quite mature, remove 

 the indusium, and with a good lens look at the spore-cases, 

 sporangia. Mount in water in the usual way, and examine 

 under a low power of the compound microscope. Observe 



1. The general form and structure of the sporangium, 



a flattened sac, the walls of which are composed of 

 distinct cells. 



2. The annulus, a row of thick-walled cells, forming a 



continuation of the stalk. Does the annulus ex- 

 tend completely around the sporangium ? 



III. Examine the sporangia under a high power, observ- 

 ing them in different positions. Compare different speci- 

 mens and draw a perfect one. 



