i8 



HEREDITY AND EVOLUTION IN PLANTS 



Fig. ig. — Germination of the spores of a fern, a, Before germination; 

 b, early stage, showing protonema (pr.), and first rhizoid (rh); c, d, e, f, 

 successive stages in the development of the prothallus. 



Fig. 20. — Prothallus of a fern. Archegonia on the (central) cushion 

 near the notch; antheridia among the rhizoids, below. (After Margaret 

 C. Ferguson.) 



