GROUP III. PTERIDOPHYTA. 353 



Class VI. EQUISETIN.E. The sporophyte is characterised 

 by the well-developed branched stem, with small whorled leaves 

 forming a sheath at each node ; the small peltate sporophylls are 

 aggregated into a cone-like flower at the apex of each fertile shoot, 

 and bear a few sporangia on the inner (inferior) surface ; the 

 archesporium is a single cell ; the embryo has a primary root 

 and no suspensor. All the existing forms are homosporous and 

 eusporangiate. 



The gametophyte is a free, green, membranous prothallium, 

 generally dioeoious ; the spermatozoids are multiciliate. 



Order 1. Equisetacece. 



Class VII. LYCOPODIN^E. The sporophyte is characterised 

 by the well-developed branched stem with numerous small 

 scattered leaves ; the sporangia are borne singly either on the 

 upper surface of a sporophyll, or on the stem ; the sporophylls 

 resemble the foliage-leaves, but are sometimes aggregated into 

 cone-like flowers; the archesporium is multicellular ; the embryo 

 has a suspensor, but no primary root. All the existing forms are 

 eusporangiate. 



The characters of the gametophyte vary widely. The sperma- 

 tozoids are biciliate. 



Sub-Class HOMOSPOREJE : the sporophyte produces spores of one 

 kind only ; the prothallia are free, more or less tuberous, mon- 

 oecious. 



Order 1. Lycopodiacece. Order 2. Psilotacea. 



Sub-Class HETEROSPORE^: : the sporophyte produces microspores 

 and macrospores ; the former give rise to male, the latter to 

 female, prothallia ; the prothallium does not become free from the 

 spore. 



Order 1. Selayinellacece. 



The relations of these various groups may be simply expressed 

 as follows : 



FILICIN^E. EQUISETIN.E. LYCOPODIN.S:. 



Homosporous Filices \Lepto- 



Heterosjiorous Hydropterideae - ' tporangiate. 



Homotporous fOphioglossacese J_ E isetacese _ fLycopodiace* j } 



iMarattiacese ) IPsilotacese ' K Eusporangiate 



Heterosporous -Isoetacese (none existing) Selaginellacese ) 



M.B. A A 



