Laffeety — Disease of Cultivated Flax. 257 



Cooked green fl.ax-eictract agar is an unsuitable medium for the growth of 

 the fungus ; the submerged mycelium is sparse, with a complete absence of 

 discoloration. Slimy, dirty white masses of conidia are produced on the 

 surface of the medium, and, to a lesser degree, conidia are formed in the 

 medium itself. They are very variable in shape and size, but average 



On all the media mentioned the conidia are produced in masses from the 

 swollen tips and along the sides of the hyphae, which are little, if at all, 

 differentiated from the ordinary mycelium, and which, therefore, scarcely 

 deserve description as definite conidiophores. On the sides of the hyphae or 

 on surface mycelium they are produced, one or more at a time, on the apices 

 of short, blunt " pegs," whicli jut out from the cell wall, but which are very 

 distinct from sterigmata ; see fig. 6, Plate X. On the ends of the hyphae, 

 which, as a rule, are slightly swollen, the conidia are produced by abstriction, 

 and they may arise at any point ; see fig. 3, Plate IX. 



It sometimes happens that if, for some reason or other, a cell of the 

 mycelium loses its protoplasm, the neighbouring cell behaves as a conidio- 

 phore, and conidia are produced in succession from it, and are pushed into 

 the empty cell. Such a case is shown in fig. 8, Plate X. 



The germination of the conidia, taken from the host as well as from pure 

 cultures, has been followed in hanging drops of tap water, of the liquid 

 extract of cooked flax, and also on film cultures of beef-extract gelatine, wort 

 gelatine, and extract of oat agar. 



In tap water, before germination, the conidia become much swollen, and 

 in many cases two-celled, by the formation of a transverse septum. This 

 causes a constriction in the middle of each conidium. Prom either or both 

 ends of the conidia new conidia are produced, but no germ tubes are developed. 



Where nutrients are used, however, the conidia swell rapidly, and in 

 almost every case a transverse septum is produced, previous to the emission of 

 a germ tube from one or both ends of the swollen conidium. As a rule these 

 germ tubes soon become branched, and begin to produce new conidia at their 

 ends after they have grown a short distance. Gradually, however, they 

 increase in length by the development of new terminal cells, and these in 

 turn bear conidia at their ends and along their sides until a fungus growth 

 results, with a small amount of mycelium, but an abundance of conidia. The 

 germination of the conidia, their subsequent growth, and the production of 

 new conidia are illustrated in figs. 2, 3, and 4, Plate X. On wort-gelatine 

 film cultures the early form of growth of the fungus is distinctly star-shaped 

 when seen under the microscope, as illustrated in fig. 2, plate IX ; but, as 

 growth proceeds, lateral branches are formed on the radiating hyphae, and the 

 star-shaped effect becomes obliterated. 



