510 



BOTANY 



PART II 



main groups of longicidal and brevicidal Leptosporangiatae, the Eusporangiatae 

 coming closer to the former ( 119 ). 



All the members of the Filices are homosporous. The PRO- 

 THALLIUM has usually the form of a small, flat, heart-shaped thallus 



FIG. 474. Trlchomanes rigidum. Portion 

 of a prothallus with an archegoniophore 

 (A) to which a young plant is attached. 

 (After GOEBEL.) 



FIG. 475. A y Mature antheridium of Woodsia 

 ilvensis ; the cuticle (c) is ruptured. B, 

 Open antheridium; d, cap-cell ; r, swollen 

 annular cells. (After SCHLUMBERGER.) C, 

 Spermatozoid of Struthiopteris germanica ; 

 k, nucleus ; d, cilia ; 6, vesicle derived from 

 the vacuole ; c, cytoplasm. ( x 850. After 

 SHAW.) 



(Fig. -461), bearing the antheridia and archegonia on the under side 

 which is turned from the light. 



In certain Hymenophyllaceae ( Trichomanes) the prothallium is filiform and 

 branched, resembling in structure the protonema of the Mosses, and producing 

 the antheridia and archegonia on special multicellular lateral branches (Fig. 474). 



The ANTHERIDIA and ARCHEGONIA ( 12 ) are similarly constructed in 

 nearly all Leptosporangiatae, and present differences from those of the 

 Eusporangiate Ferns. The antheridia are spherical projecting bodies 

 (Fig. 475), arising on young prothallia by the septation and further 

 division of papilla-like protrusions from single superficial cells. When 

 mature, each antheridium consists of a central cellular cavity, filled 



