150 ASPIDIU3.I ACROSTICHOIDES. CHRISTMAS SHIELD-FERN. 



bearing them on his wings he fixes them Hke verdant stars on 

 the summit of some old castle, or, disposing them in light fes- 

 toons, adorns with them the refreshing and shady spots which 

 shepherds love. Thus it is that this wild plant conceals its 

 secret origin from the most penetrating eyes, but anxiously 

 replies with benefits to the curious search of the permitted 

 inquirer." 



At the present time, indeed, we know much more about the 

 secrets of the fern than our ancestors did ; but still it must be 

 said that even now botanists are not quite agreed as to what 

 they see, at least in so far as the classification of ferns is con- 

 cerned. Most American botanists regard the species to which 

 this chapter is devoted as an Aspidium, but John Smith, a noted 

 English pteridologist, that is to say, one versed in the knowledge 

 of ferns, still regards it, as Michaux did, as a Nephrodmm. 

 Roth, a German botanist, who flourished about the end of the 

 last century, and was one of the first to point out the value of 

 the indusium (the membrane which covers the fruit-dots or sori 

 in most ferns) as a character in the classification of ferns in 

 determining genera, placed our plant in the genus Polystichum, 

 which he had himself instituted. Dr. Gray, however, merely 

 regards Polystichtun as a subdivision of Aspidiiim. 



When the value of the indusium had come to be fully under- 

 stood, the species here illustrated and its allies were classed 

 together in the genus Aspidium, owing to the peculiar character 

 of the indusium, which at a certain stage in the life of the plant 

 has the appearance of a little shield. In the earlier condition of 

 the fertile frond the edge of the circular indusium which protects 

 the sporangia, and which is simply part of the cuticle of the 

 frond, adheres closely to the pinna (see Fig. 3) ; but later in the 

 season these sporangia or spore-cases burst through the indusium 

 at all points of its circumference, leaving its membrane attached 

 to the pinna by the middle only, thus giving it the shape of a 

 little umbrella, or, as the Greek name Aspidioit implies, of a 

 little shield. In all ferns, indeed, the spores are formed beneath 



