ACROGEN^. 703 



Sub-kingdom II. 



CRYPTOGAMIA, ACOTYLEDONES, OR FLOW- 

 ERLESS PLANTS. 



Class IH. ACOTYLEDONES. 

 Sub-class I. Acrogence, 



Natural Order 286. Filices. — The Fern Order. — Herbs, 

 with rhizomatous stems {fig. 158), or arborescent plants {fig. 

 159). Leaves, or fronds as they are commonly called, arising 

 irregularly from the rhizome {fig. 158), or placed in tufts at the 

 apex of the stem {fig. 159); almost always circinate in vernation 

 {figs. 158, 159, and 273); simple or compound {figs. 158 and 

 782). Fructification consisting of sporangia {figs. 780 and 

 781), collected in heaps {sori^ usually on the under surface or at 

 the margin of the fronds, or rarely on the upper surface, or oc- 

 casionally in a spiked manner on a simple or branched rachis 

 {fig. 782) ; the sori are either naked {fig. 780), or covered by 

 a membranous scale (indusium), {fig. 781). Sporangia stalked 

 {fig. 783), or sessile, and either annulate {fig. 783), or exannu- 

 late. Spores enclosed in the sporangia {fig. 783). (For further 

 particulars upon the fructification of Ferns, see pp. 368 — 

 371.) 



Division of the Order, Sfc This order is commonly divided 



into three sub-orders, which are frequently regarded by botanists 

 as separate orders. 



These sub-orders are called Polypodiese, Danseeag, and Ophio- 

 glosseee. Their distinctive characters are as follows : — 



Sub-order 1. Polypodiece or Polypodiacece. The Polypody Sub- 

 order, or Ferns proper {figs. 780—783). Fronds circinate 

 in vernation. Sporangia more or less annulate, collected in 

 sori on the under surface or at the margin of the fronds ; or 

 arranged in a spiked manner on a simple or branched rachis. 

 Examples : — Ceterach, Polypodium, Aspleniura, Lastraea, 

 Alsophila, Parkeria, Hymenophyllum, Mertensia, Schizaea, 

 Osmunda. 



Sub-order 2. Danceeee or Danceacea. The Danaea Sub-order. — 

 Fronds circinate in vernation, and all fertile. Sporangia 

 arising from the surface, or imbedded in the under surface 

 or back of the fronds, more or less united, exannulate. Ex- 

 amples ; — Danaea, Marattia. 



Sub-order 3. Ophioglossece or Ophioglossacece. The Adder's 

 Tongue Sub-order {fig. 1087). Fronds not circinate in 



