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ROTTENNESS OF TURNIPS AND SWEDES. [Sept. 1896. 



ROTTENNESS OF TURNIPS AND SWEDES IN STORE. 



By Prof. M. C. Potter, M.A., F.L.S,, Durham College 

 of Science. 



On opening the pits or camps in which swedes* have been 

 stored during the winter it is frequently found that many of the 

 roots are quite rotten : this was especially the case in the neigh- 

 bourhood of Newcastle-upon-Tyne, in the spring of 1895, and 

 similar conditions were observed in many pits in the spring of 

 the present year. This rotten state of the roots is generally 

 attributed to the action of the frost, but, as will appear later, 

 the severity of the weather is not the chief agent in causing 

 the decay. Some of the roots are quite soft and reduced to pulp 

 with a mo3t offensive smell, others when cut open may be found 

 partially sound with the rotting portion showing a brown dis- 

 colouration. The latter are covered at their extremities with a 

 thick felt of grey mould, sometimes extending over the whole 

 surface of the root, from which a fine cloud of dust arises when 

 shaken; at the same regions numerous small, black, or dark 

 purple bodies, varying in size and of irregular shape, may also 

 be observed. 



No single cause can be found to explain these appearances, 

 the soft, rotten roots are found infested with innumerable 

 bacteria, but how far these are responsible for the decay and to 

 what extent actual freezing is accountable are questions which 

 cannot at present be answered, but in the case of the roots 

 covered with the grey mould I have been able to trace the decay 

 to a definite filamentous fungus. f 



An examination of the partially rotten roots with the micro- 

 scope reveals the presence of numerous hyphse, rich in protoplasm, 

 pervading the whole mass and branching in all directions. The 

 grey mould, on microscopical examination, is seen to consist of a 

 number of filaments projecting into the air. These filaments 

 branch near the apex (Fig. 8) and bear a number of conidia, 

 which are visible to the naked eye as the tiny cloud of dust 

 already mentioned. The branching of the filaments which bear 

 the conidia, and the character of the conidia themselves, show 

 that we have here a fungus belonging to the genus Botrytis (of 

 the section Polyactis). 



The fungi which are comprised in the genus Botrytis are very 

 common and include some of the most destructive forms. In 

 many cases it has been shown that the same fungus may have 



* Swedes are generally mentioned in the text as they are more commonly stored in 

 the pits, but wherever spoken of they may be understood to iuclude turnips ; in fact, 

 the latter are more readily attacked by the disease. 



f A filamentous fungus consists of a number of thread-like cells or hyphse, a 

 collection of these being known as a mycelium ; reproduction is effected by means 

 of special cells which may germinate and give rise to a new fungus, these according 

 to their mode of origin being termed conidia, spores, ascospores, &c. 



