XIII.] 



ABOUT FUNGI. 



185 



prolongation, ultimately developed into a sporan- 

 gium or ascus, containing many ascospores. This is 

 termed the " alternation of generations" and is similar 

 to the process of reproduction in ferns, previously 

 explained. A fern produces spores, one of which 

 germinating, gives rise, not to another fern but to a 

 minute plant called a " prothallus," which bears anthe- 

 ridia and archegonia. The former fertilise the latter, 

 and as the result of such fertilisation a bud is formed 

 which develops into a perfect fern. 



We have seen that these low forms of fungi increase 

 by cell-division, but only in one direction ; the cells 



FIG. 139. 



never divide laterally. This we shall find is a char- 

 acteristic of all fungi, and we may see by examin- 

 ation of a mushroom or toadstool that the thickness 

 of their stems is attained by the growth of many 

 hyphae side by side. Like Penicillium and Mucor 

 these larger plants arise from spores, which on 

 germinating give off hyphae, branching and inter- 

 lacing to form a mycelium. Fig. 139 illustrates the 

 development of an Agaric or Mushroom. A shows 

 the mycelium (my) with two little roundish protube- 

 rances (//), the future hymenopJiore. B is a section of 



