504 



HUTCHINSON'S POPULAR BOTANY 



the archespore, and from it is de- 

 veloped the sporogenous tissue, which 

 divides and subdivides into the mother- 

 cells from which the spores originate. 



The Vascular Cryptogams (Pterido- 

 phyta) are divided into the following 

 Classes and Orders : 



PTERIDOPHYTA. 



CLASS 



I. Filicinse 



ORDER 



1. Filices, or Ferns. 



2. Hydropterideae, or 



Water-ferns. 



II. Equisetinae 3. Equisetaceae, or Horse- 

 tails 

 III. Lycopodinae 4. Lycopodiaceae, or Club 



The scale-like body that results from the 

 of a fern-spore, (a) Archegonia. (r) 



germination 

 tootle ts. 



5. Selaginellaceae, or Sela- 

 ginellas and Quill- 



FIG. 641. A PKOTHALIJUM. 



The Order Filices or Ferns is the 

 best-known of all the Cryptogams 

 and most of its families have been well worked out. They are chiefly 

 perennial herbs (very few annual), though 

 some have shrubby stems or root-stocks, 

 and the tree-ferns are arborescent. Their 

 leaves, or fronds, may be simple, as in the 

 case of the Common Hartstongue (Scolo- 

 pendrium vulgare, finely subdivided like 

 those of the Bracken (Pteris aquUina), or 

 divided to any intermediate extent. The 

 sporanges are borne in clusters (sori} of 

 various kinds on the back or the margins 

 of the frond, and are usually placed above 

 a vascular bundle. The sorus is often 

 protected by an indusium, which is an 

 outgrowth from the epiderm and may be 

 two-valved, cup-shaped, linear, hood-like, 

 buckler-shaped, kidney-shaped, or a con- 

 tinuation of the frond margin. In some 

 species the sori are produced on special 

 fronds, which may differ in appearance 

 from the barren fronds, as is the case with FIG. 642. FERN-SPORES GERMINATING. 

 our Hard Fern (Lomaria spicant, fig. 637) T he erst figure shows the shoot with rootlet 

 and Parsley Fern (Cryptogramme crispa}. bursting through the exospore. The second shows 



'. , a more advanced stage, and the division of cells 



In germination the exospore bursts and toformtheprothaiuum. 



