OKGANOGRAPHY. 55 



and exammlate 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 

 Polypodiaceae). 



2. Sporangium with a horizontal ring, mag. 100 diameters (sub- 



order Gleicheniacese). 



3. Sporangium with an apical ring, mag. 100 diameters (sub-order 



Osmundacese). 

 (a.) Spores of each highly magnified, 200 and 300 diameters. 



Exannulate (Order Marattiacse) 



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 (Dansea). 



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 calyciform, slightly magnified (Cyathea). 



10. Indusium linear, interiorly attached, slightly magnified (Asple- 



nium). 



11. Indusium valvate, slightly magnified (tribe Dicksoniieae). 



12. Indusium universal, slightly magnified (Strutbiopteris). 



