CHAPTER X. 



REPRODUCTION OF THE FERN SPORANGIA PROTHALLUS 

 EMBRYOLOGY. 



Sporangia and spores. 



The plant of which the general structure has now 

 been described, and which is known as the sporophyte, 

 bears certain reproductive cells which are called spores. 

 The development, and structure, of the spores, must now 

 be given in detail, together with the history of their 

 germination ; this will be followed by an account of the 

 oophyte to which the germinating spore gives rise. 



The spores (as in the case of Mucor) are found in 

 receptacles sporangia of which a group is shown in 

 fig. 57. The sporangia grow in groups and patches 

 known as sori, which in the majority of ferns are found 

 on the lower surface of the leaves. Each sorus is pro- 

 tected by a covering, the indusium. In Pteris the 

 indusium is the edge of the leaf folded back so as to roof 

 over the linear sorus running down the marginal part of 

 the leaf. In Aspidium it is a specially developed mem- 

 brane covering the sorus like an umbrella, and therefore 



P. E. B. 9 



