84 Prof. Marshall Ward, Rust-fungi and "Mycoplasm" Hypothesis. 



Rust-fungi and the " Mycoplasm " Hypothesis. By Professor 

 H. Marshall Ward, D.Sc, F.R.S., Sidney Sussex College. 



[Bead. 16 February 1903.] 



The author gave a brief account, illustrated with lantern slides 

 and microscopic preparations, of that part of his researches into 

 the histology of Rust-fungi which bears upon the recent pronounce- 

 ment of Eriksson, that certain corpuscules speciaux observable in 

 the cells of the host-plant, are the assumed " mycoplasm " in the 

 act of growing out to form the hyphse of the fungus. 



The author's preparations show clearly that Eriksson's cor- 

 puscules are true haustoria, put forth by the hyphse of the fungus 

 into the cells of the host. Every stage in their development is 

 traced, and since the entering germ-tube, after swelling up as an 

 infecting vesicle and tube in the stomatal cavity, is found to put 

 forth one of these haustoria at a very early date, the reversed 

 order of the phenomena assumed by Eriksson cannot be accepted. 



