ORGANOGRAPHY. 
55 
and exannulate Ferns in cultivation in this country 
are in proportion to one another as one to forty-five, 
he may soon become aware that the great majority 
of Ferns belong to the annulate section. But the 
best way for a beginner is to procure a few correctly- 
named species of each tribe, and carefully compare 
them with the characters given in the following 
pages. He will soon overcome the dread of technical 
phrases, and before long will be able to refer his 
unnamed species to their respective tribes and 
genera. 
EXPLANATION OF THE PLATE. 
Annulate Sporangia — 
Fig. 1. Sporangium with a vertical ring, mag. 100 diameters (sub-order 
Polypod iaceae). 
2. Sporangium with a horizontal ring, mag. 100 diameters (sub- 
order Gleicheniacese). 
3. Sporangium with an apical ring, mag. 100 diameters (sub-order 
Osmundaceae). 
(a.) Spores of each highly magnified, 200 and 300 diameters. 
lixannv.la.te (Order Marattiacre) — 
Fig. 4. Sporangia (two) free, opening by a vertical slit, mag. 25 dia- 
meters (Angiopteris). 
5. Sporangia united (synangium), opening by pores, mag. 7 dia- 
meters (Danaea). 
6. Sporangia united (synangium), opening by slits, mag. 9 dia- 
meters (Marattia). 
(a.) Spores of each highly magnified, 300 diameters. 
Jndusia — 
Fig. 7. Indusium peltate orbicular, slightly magnified (Aspidium). 
8. Indusium lateral reniform, slightly magnified (Nephrolepis). 
9. Indusium oalyciform, slightly magnified (Cyathea). 
10. Indusium linear, interiorly attached, slightly magnified (Asple- 
nium). 
11. Indusium valvate, slightly magnified (tribe Dicksoniieoe). 
12. Indusium universal, slightly magnified (Struthiopteris). 
