502 BOTANY TART n 



fronds. Sporangia either on the under side of the sporophylls, 

 united in sori or free, or enclosed in special segments of the leaves. 

 Spermatozoids multiciliate. 



Sub-Class ]. Filicinae eusporangiatae. Kipe sporangia with firm 

 wall composed of several layers of cells. Homosporous. 



Sub -Class 2. Filicinae leptosporangiatae. Ripe sporangia with 

 walls one layer thick. 



Order 1. Filices. Ferns, in the narrower sense. Homosporous. 

 Order 2. Hydropterideae. Water-Ferns. Heterosporous. 



2. Equisetinae. Horse-tails. Stem simple or verticillately branched, 

 with whorled, scale-like leaves forming a united sheath at each node. 

 Sporophylls peltate, bearing a number of sporangia on the under side, 

 and aggregated into a cone at the apex of each fertile shoot. 

 Spermatozoids multiciliate. 



Order 1. Equisetaceae. Horse-tails. Homosporous, herbaceous 

 plants. 



Order 2. Calamariaceae. Calamites. Homosporous or hetero- 

 sporous. Extinct arborescent plants. 



3. Sphenopliyllinae 



Order 1. Sphenophyllaceae. Stem slender; leaves in whorls. 

 Sporophylls with 1-4 sporangia, borne in cones. Homo- 

 sporous. Extinct plants. 



4. Lycopodinae. Stem simple or dichotomously branched. Roots 

 dichotomous. Leaves alternate, simple. Sporangia with firm walls, 

 always borne singly in the axils of the sporophylls. 



Order 1. Lycopodiaceae. Club -mosses. Homosporous ; sper- 

 matozoids biciliate ; herbs with dichotomously branched 

 shoots. 



Order 2. Psilotaceae. Homosporous ; stem herbaceous, dichoto- 

 mously branched, with alternate, simple, or scale-like leaves ; 

 rhizomes in place of roots ; sporophylls forked, each bearing on 

 the adaxial face close to its base a 2- or 3-locular sporangium. 



Order 3. Selaginellaceae. Heterosporous ; Spermatozoids bicili- 

 ate ; herbs with dichotomous stems and small leaves. 



Order 4. Isoetaceae. Quill-worts. Heterosporous ; spermato- 

 zoids multiciliate ; stem tuberous, simple, with secondary 

 thickening ; leaves awl-shaped. 



Order 5. Sigillariaceae. Extinct. Heterosporous ; arborescent ; 

 stem simple or sparingly branched dichotomously. 



