152 ASPIDIUM ACROSTICHOIDES. CHRISTMAS SHIELD-FERN. 



was at one time believed to extend to the Pacific coast, and to 

 have been collected there by Menzies ; but the species found by 

 him, although closely related to our fern, is now regarded as a 

 distinct form, and is called A. auriculatum. 



Our plant has its home in the states east of the Mississippi, 

 or as Mr. Redfield expresses it, in the Appalachian geographical 

 group. It is found in almost all the states of this group, from 

 the Great Lakes to the Gulf of Mexico ; and should occasion 

 arise at any time for the adoption of a fern as a national em- 

 blem, none could probably be found to meet the requirements 

 better than this. 



Many ferns have their fruit-dots on fronds nearly or quite like 

 those which are barren, while others have them on fronds differ- 

 ing entirely in character from the sterile fronds. It is interest- 

 ing to note that the Christmas Shield-Fern is intermediate 

 between these two classes The fruiting fronds of our species 

 are merely a little more incised or cut-toothed on the edges, and 

 even in these fronds, only the upper portion, on which the fruit 

 appears, has this character, while the lower portion, which bears 

 no sori, is like the barren ones. Sometimes all the fronds, bar- 

 ren as well as fertile, are incised, which condition was formerly 

 supposed to denote a distinct species, named A. Schzvciiiitzii, 

 but this distinction has now been abandoned. 



In an average-sized pinna there is but a single row of sori on 

 each side of the midrib, but in tlie stronger ones there is gener- 

 ally a double row, and at the season of maturity the whole back 

 is covered with the sporangia. 



Explanation of the Plate. — i. A plant rather below the medium size. — 2. Pinna from 

 a male frond, showing the disposition of the veins. — 3. Pinna from the fertile portion 

 of a frond, just previous to the bursting of the sporangia through the membrane of the 

 indusium, and e.xhibiting its more deeply cut margin. 



