THE PTERIDOPHYTES 



283 



363. Asexual Reproduction, Spore-Cases and Spores.^ — Pick out 

 some spore-cases from a sorus (Fig. 204, C, D), mount them in -water, 

 examine with l.p., and note : 



(a) The stalk. 



(6) The spore-cases proper. Draw. 



(c) The partial ring of thick-walled cells enclosing the siDore-case. 



(rf) The spores. These should also be examined with h.p. Draw. 



The spores are scat- 

 tered by the splitting 

 open of the spore-case 

 when very dry, pulled 

 apart Xij the elastic ring 

 (Fig. -204, D). 



364. The Gameto- 

 phyte (Prothallium) and 

 Sexual Reproduction. — 

 Material for this study 

 may be obtained by 

 dusting spores of any 

 desired species of fern 

 over bits of brick or 

 broken flower-pots or 

 earth kept moist under 

 a bell-glass. The spores 

 of most genera are long- 

 lived and germinate 

 readily many months 

 after they mature. They 

 should be sown six 

 weeks or more before 

 the material is needed 

 for class use. Germinating spores in all stages of development may 

 also be found on flower-pots containing greenhouse species of fern, 

 particularly Adiantum. Mount some of the material, examine A^ith 

 h.p., and note : 



(a) Several stages in the germination of spores. Draw. 



Fig. 205. Prothalliumof aFern(PoZ2/s<Jc^Mm). 

 View of the under surface. 



gp, growing point; ar, archegonia; an, anther- 

 idia ; rh, rhizoids ; *•, region in which the spore 

 germinated. (X about 8.) 



1 Polypodium is excellent material for the study of the sporangia, 

 minute structure of the vegetative ^portion of the fern is here omitted. 



The 



