MYCOPLASM 161 



plasm of the host, in the 'seed.' To this mixture of 

 protoplasm of parasite and host Eriksson has applied the 

 name of mycoplasm. When such infected seed is sown 

 the fungus protoplasm remains unchanged until the plant 

 has produced leaves, when it materialises, or separates 

 from the protoplasm of the host, and forms structures 

 termed ' special corpuscles ' in certain cells of the host- 

 plant, at those points where uredo-pustules will eventually 

 appear. These special corpuscles are described by 

 Eriksson as occurring mixed with the other elements of 

 the cells, most frequently oblong in form, sometimes 

 slightly curved. Some of these bodies lie free in the 

 protoplasm of the cell, others are attached to the cell-wall 

 of the host, which they pierce and form outside an in- 

 tercellular mycelium. This intercellular mycelium even- 

 tually gives origin to a sorus of uredospores. 



This remarkable theory has been thoroughly investigated 

 by Ward, who has shown that Eriksson's special corpuscles, 

 considered as the first products of materialisation from 

 mycoplasm, are in reality nothing more than ordinary 

 haustoria that have entered certain cells from intercellular 

 mycelium, itself the product of external infection caused 

 by germinating uredospores. Hence the mycoplasm 

 theory appears to be altogether unsupported by facts, 

 although it must be stated that the idea is not yet aban- 

 doned by its originator. 



Eriksson, Compt. Rend., 124, p. 475 (1897). 



Ann. Soc. Nat., ser. 8, 15, p. 193 (1902). 

 Ward, Phil. Trans. Roy. Soc., 196, p. 29 (1904). 



