456 THE RED STRING OF THE SUGAR-CANE, 



These rose at right angles to the plane of the glass and appeared 

 to be of the nature of haustoria. Like the hypha^ of the ground 

 mycelium, they were capable of penetrating other h3'pha?, but, as 

 they rose vertically, they did not have the same chances of doing 

 so. 



When the growth reached a maximum, some of the cells which 

 constituted the anastomosing mycelium became thinner and less 

 refractile, while other cells or groups of cells became stouter and 

 the walls thicker. These thickened cells, however, were no more 

 resistant to the entry of the growing point of a h3^pha than the 

 ordinary cells, for the point could enter and abstract the contents 

 not only of the cell which was entered but also of its neighbours, 

 thus indicating that the individual thickened cells although 

 divided by a septum were still in communication. These 

 thickened cells were apparently of the nature of oidia. 



In solutions of sugar such as Hansen's fluid no further develop- 

 ment was observed, but in nutrient bouillon the thickened cells 

 became gradually spherical, dark-coloured, and very granular. 

 Sometimes single cells developed in this way, but generalh' 

 several adjoining cells began to change (PI. xiii., figs. 1-2). After 

 becoming dark and opaque, many of the cells divided, usually at 

 right angles to the direction of the original hypha, but not always 

 so. Frequently these secondary cells again divided, and either 

 became spherical or remained attached as hemispheres, forming a 

 small moruloid cluster of cells. At this stage the growth ceased 

 in the damp chambers. 



It will be remembered that black patches appeared upon the 

 surfaces of sterilised potato and sugar-cane which had been 

 infected with the mould. Under a low magnification these ap- 

 peared intensely black, dull or slightly shining, rough and moru- 

 loid, apparently consisting of a collection of irregular spheres 

 (PI. xiii., fig. 3). They were brittle, and under pressure broke up 

 into opaque fragments, at the same time liberating a multitude 

 of minute, colourless, egg-shaped spores, each measuring 5 : 3/i 

 (PI. xiii., fig. 4). In order to gain an idea of the structure of 

 these spore-cases or perithecia, paraflin sections of a potato culture 



