352 PART IV. CLASSIFICATION. 



gametophyte (prothallium) multiplies vegetatively by means of 

 gemmae, which are short spindle-shaped rows of cells in the one 

 case, and globular multicellular bodies in the other. 



The Life-History of the Pteridophyta presents in all cases, a 

 perfectly clear alternation of generations, the sporophyte and the 

 gametophyte being completely distinct. The oospore developes 

 into "the plant," be it Fern, Equisetum, or Lycopod, which bears 

 the sporangia and spores, and is the sporophyte. The spores, 

 when shed, germinate to form the gametophytes (prothallia) bear- 

 ing the sexual organs. 



The Pteridophyta are classified as follows : 



Class V. FILICINJ3. The sporophyte is characterised by 

 having relatively large and few leaves ; the sporophylls are gener- 

 ally similar to the foliage-leaves and are not aggregated into 

 flowers ; the sporangia are numerous on the sporophyll (except 

 Isoetes) and are arranged in sori ; the archesporium is a single 

 cell (except Isoetes); the embryo has a primary root (except 

 Isoetes, Salvinia, and possibly some species of Trichomanes) but 

 no suspensor. 



The characters of the gametophyte vary widely. The sper- 

 matozoids are multiciliate. 



Sub-Class Eusporangiatae. Each sporangium is developed 

 from a group of superficial cells. 



HOMOSPORE.E. 

 Order 1. Opliioglossacece. Order 2. Marattiacea?. 



HETEROSPORE.E : Order 1. Isoetacese. 



Sub-Class Leptosporangiatae. Each sporangium is developed 

 from a single superficial cell. (Filices in limited sense.) 



HOMOSPORE^. 



Order 1. Osmundacece. Order 4. PolypodiacecK. 



2. Schizceacece. ,, 5. Cyatheacece. 



,, 3. Glcicheniacece. ., 6. HymenophyllacecK. 



HETEROSPORE^E. 

 Order 1. Snlviniacecr,. Order 2. Marsileaccai. 



