Fig. 196. Nephrodium Filix mas.

A. Pinnule with nine sori (a).
B. Magnified portion of pinnule with the sporangia. a. Stomata. b. Sporangia partially covered by c. the indusium.
C. Magnified sporangium. a. Stalk. b. Ring. c. Membranous sac.
D. Ruptured sporangium, with the spores escaping.

This image is from Male Fern in Pereira's Elements of Materia Medica and Therapeutics, 1854.