256 Scientific Proceedings, Royal Dublin Society. 



showed the production of new conidia from their ends. The gelatine is 

 slowly liquefied, the process not being complete even after four weeks. 

 Agar is not affected. 



Cold water exiraci of Quaker-oat agar is a poor medium for the growth of 

 the fungus. The amount of mycelium produced is relatively small, but dirty 

 white masses of conidia are produced in good amount on the surface of the 

 medium. The conidia averaged 13-7^ x ifj. in length and breadth respectively ; 

 and in shape they closely resembled those produced on the host plant. 



Ground Quaker-oaf agar was found to be the best medium for long- 

 continued growth. On it the fungus grows slowly, but continues growing 

 until the entire surface of the slant is covered, this being accomplished in 

 about one month. The mycelium is again submerged, and conidia in cream- 

 coloured, slimy masses are produced in abundance on the surface of the 

 medium. After growing for several days, the submerged mycelium gradually 

 becomes dark in colour, and as time goes on this darkening increases in 

 intensity until a dense wrinkled mass of matted black mycelium is produced 

 at or immediately below the surface. When examined microscopically, the 

 dark mycelium is found to consist of much-swollen, more or less spherical 

 thin-walled cells, with finely granular contents. Individually these cells are 

 olive brown in colour, but when seen in mass the effect produced is almost 

 black. The individual swollen cells of this dark mycelium eventually break 

 away from one another, but their subsequent behaviour was not followed. It 

 is believed, however, since they have never been seen in the tissues of the 

 host plant, and are produced only on certain nutrient media, that they have 

 no special significance in the bionomics of the fungus. Occasionally the olive 

 tinge was taken up by the conidia or was diffused into the substance of the 

 medium. As a rule, however, the conidia are hyaline, except where they are 

 in intimate contact with the dark hyphae, and they averaged 14-5^( x 4-l;u in 

 length and breadth respectively. 



The fungus grows well on cooked green flax stems, and produces acervuli 

 on their surfaces. These acervuli are only Just visible to the naked eye as 

 very minute black dots resembling pycnidia. Microscopical examination 

 shows that each conidial mass is in reality hyaline or milky in appearance, 

 but, as it is seated on a dark-coloured base made up of the conidiophores 

 whose swollen apices in this case are olive-coloured,- it appears to have a 

 smoky tinge. The conidia in the acervuli are similar to those found on the 

 living host, and average H-Sjn x 3'8/i. 



The mycelium in the tissues of the cooked flax stems is thick, hyaline, and 

 much septate, the darkening only showing where the conidiophores burst 

 through the epidermis. 



