384 Scientific Proceedings, Royal Dublin Society. 



Fig. 



5. Treatment of naturally infected seed with formalin. In each pot one 



hundred seeds were sown. Those in the left-hand pot were steeped 

 for two minutes in 40 per cent, formalin 1 : 400, and gave rise to 

 ninety healthy, and three diseased, seedlings. Those sown in the 

 right-hand pot were not treated, and gave rise to one healthy plant 

 and ninety-three diseased plants, most of which were completely dead 

 at the time of photographing. 



6. Portions of the hypocotyledonary stems of three flax seedlings, derived 



from artificially infected seed, showing lesions of Colletotrichum 

 linicolum on their surfaces. (Slightly reduced.) 



Plate XX. 



1. Eipe conidia and germinating conidia of Colletotrichum linicolum from a 



pure culture, (x 730.) 



2. The growth from a single conidium on an oat-extract-agar film after five 



days, showing the production of conidiophores and conidia, and the 

 development of appressoria. (x 510.) 



3. A conidium which has germinated on the surface of a flax stem. An 



appressorium was first produced, and from its lower surface a delicate 

 hypha penetrated into the epidermal cell as shown, (x 730.) 



4. Appressoria developed from mycelium in contact with the sides of a 



test-tube in a three weeks' old pure culture of C. linicolum on oat- 

 extract-agar. (x 730.) 



5. Setae of the fungus ; on the left from a naturally infected leaf, on the 



right from a pure culture, (x 510.) 



6. Conidiophore and conidia formed within an empty cell of a hypha. 



(x 510.) 



7. Portion of section through the endosperm and seed-coat of an infected 



flax-seed showing hyphae of O. linicolum in the swollen epidermis, 

 (x 510.) 



