310 



METHODS IN PLANT HISTOLOGY 



The older roots of Botrychium., especially the large fleshy roots of 

 B. obliquum, cut very easily and show a simple exarch protostele with 

 4 or 5 protoxylem points. 



The roots of Angiopteris and Marattia, which become as large as a 

 lead pencil, may be secured in some greenhouses. Since fine large roots 

 are exposed above the soil, gardeners will generally furnish a root, 



although they might hesitate 

 to dig into the soil for such a 

 large root. They cut easily 

 after fixing in formalin alcohol 

 and furnish a fine example of 

 the exarch protostele, common 

 to all roots (Figs. 99 and 100). 

 Even such big roots as these 

 need no treatment with hydro- 

 fluoric acid. 



The structure of the leaf will 

 appear in sections cut to show 

 the sporangia. 



The sporangia. — To iflus- 

 trate the character of the an- 

 nulus, select sporangia which 

 are just beginning to turn 

 brown and mount them whole. 

 Fix in formalin acetic alcohol, 

 and dehydrate as if for paraffin 

 sections; after the absolute al- 

 cohol, transfer to 10 per cent 

 Venetian turpentine. Staining 

 is neither necessary nor desir- 

 able. The various kinds of an- 

 nulus which characterize the 

 seven time-honored famflies— the vertical, oblique, apical, equatorial, 

 and rudimentary— are easily demonstrated in such mounts. 



The various relations of sorus and indusium are best illustrated by 

 rather thick sections (10-20 /x) of material in which the oldest sporan- 

 gia have barely reached the spore stage. Fix in formalin alcohol and 

 stain in safranin and anilin blue. 



For the development of sporangia any of our common ferns will 









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Fig. 99. — Angiopteris evecta: photomicrograph 

 of a transverse section of a root, showing the poly- 

 arch, exarch siphonostele. Eastman Commercial 

 Ortho film, Wratten E filter (orange); arc light; 

 J. Swift and Son 1-inch lens; exposure, l second. 

 Negative by Dr. P. J. Sedgwick. X25. 



