282 ESSENTIALS OF BOTANY 



leaves. In some cases the spore-bearing leaves are ar- 

 ranged in spherical cones (Fig. 213), while in others 

 spores are borne by the ordinary leaves scattered along 

 the stem. 



361. Occurrence of Ferns. — Many of our commonest 

 ferns are shade-plants, flourishing in moist woods, but 

 there are widely distributed species, such as the bracken 

 fern {Pteris aquilina), which grow readily in full sunshine. 

 A few, such as Notholcena, Qryptogramma, Polystichum, 

 and Pellcea, are decided xerophytes, growing usually on 

 nearly bare rocks. Some species are highly local in their 

 distribution, occurring only in a few localities, often of 

 very limited area. 



ASPLENIUM, A FERN 



362. Gross Structure.^ — Using fresh or preserved material for tlie 

 underground portion and fresh material or dried and pressed herba- 

 rium sheets ^ for the portion above ground, note : 



(a) The color, size, shape, and appendages of the rootstock. 



(b) The mode of development of the leafy portion of the plant 

 from the rootstock (Fig. 204). 



(c) The mode of origin of the leaves, or fronds, from the root- 

 stock and their general form and the amount and manner of division. 

 The main axis is called the rhaclds, the leaflets pinna:, and their sub- 

 divisions j«'n)i»/es. Draw a leaf. 



(</) The sori, or frult-dols, on the under surface of the leaves.' 

 Draw a group of sori, as seen with the magnifying glass. 



1 This outline applies in detail only to Asplenutm fillx-fainlna, a sjjecies 

 common in moist woods, tliough with slight modifications it will apply to any 

 Asplenium and, in cousiderahle part, to most genera. 



2 Fronds, or parts of fronds, may also be mounted like passepartout-ix&-me& 

 pictures, between two sheets of glass, and are very convenient to pass from 

 hand to hand, showing both sides of the frond. 



3 In the bracken fern (Pteris) and the maidenhair fern (Ailiantum) the 

 spore-cases are borne near the edges of the leaves and covered by the incurved 

 edges of the frond. 



