252 Scientific Proceedings, Royal Dublin Society. 



brown and disorganized, while the chlorophyll granules are destroyed. 

 Cross-sections of flax stems in the early stages of the disease show fvxngus 

 hyphae permeating the parenchymatous tissues of the cortex and travelling 

 in the cells between the fibre bundles. Fungus hyphae have never been 

 observed penetrating the fibre bundles themselves or extending into the 

 wood. A cross-section through a partially diseased stem is shown in 

 Plate VIII, fig. 4. 



In such cross-sections the individual fibres of the bundles running 

 through a diseased portion of the stem usually have somewhat thinner walls 

 and larger lumina than those of normal fibres in a liealthy region of the 

 stem. Owing to the shrinkage consequent on the death of the epidermal 

 and cortical cells, the fibres are somewhat flattened tangentially. 



Micro-chemical tests show that the fibre bundles in a diseased region 

 undergo certain changes in composition. Thus, with Schulze's solution, the 

 thickened parts of the fibre walls slowly become violet in colour, while the 

 middle lamellae are stained yellow. The walls of normal fibres when treated 

 with this reagent quickly become blue, 'while the middle lamellae remain 

 undifferentiated. When cross-sections are treated with concentrated 

 sulphuric acid, the thickened walls of the fibres in a diseased region swell up 

 and become dissolved ; but the middle lamellae remain insoluble, and present 

 the appearance of a brown cellular skeleton. In a healthy region the middle 

 lamellae also disappear. With a solution of iodine in potassium iodide the 

 middle lamellae of the fibre bundles in a diseased region are coloured yellow, 

 while the thicker portions of the fibre walls remain unstained. Phloroglucin 

 stains the wood a bright red in all regions ; but in a diseased region it also 

 stains the middle lamellae of the fibre bundles red, whilst the walls of the 

 individual fibres themselves are also to some extent reddened. This does not 

 occur with normal fibre bundles ; and the reactions suggest that lignification 

 of the walls of the fibres has to some extent occurred. Correlated with this 

 change is, doubtless, the fact already alluded to, that at diseased regions 

 the stems become somewhat brittle. 



Since, as will be seen later, the disease is one which is transmitted by 

 means of the seed, special attention was paid to the manner in which the 

 seeds become infected with the fungus. For this purpose, fruits at all stages 

 of development were collected and studied microscopically by means of cross- 

 sections. The progress of the mycelium was traced from the outside of the 

 fruit through the tissues of its walls to the placenta, until it reached the seed 

 itself by traversing the extremely short funicle. If the seeds are young, and 

 the several layers of the seed-coat consequently not fully developed, the 

 fungus penetrates these tissues, and reaches the young embryo, which becomes 



