Sept. 1896.] ROTTENNESS OF TURNIPS AND SWEDES. 



121 



two distinct methods of reproduction and hence appear under 

 totally distinct forms, which were thus often described under 

 different names before their connection had been established. 

 The fungus in question affords a very good example, one of its 

 stages being known as Botrytis and the other as Feziza (Sclero- 

 tinia). In the one stage, which may be termed the conidial 

 stage, a number of conidia — small oval bodies — are produced on 

 branches of the mycelium projecting into the air. The conidia 

 are reproductive cells which, under favourable conditions, ger- 

 minate, protruding a germ-tube (Fig. 1) capable of growing 

 into a new fungus. The production of conidia may last for some 

 time, but eventually the time comes when the fungus is no longer 

 capable of producing them, and the small black bodies previously 

 mentioned commence to be formed. These bodies consist of a 

 number of fungal hyphse which have branched repeatedly until 

 they have become firmly wefted together to form a compact 

 structure known as a sclerotium, white at first, but when mature 

 assuming the characteristic dark colour. The sclerotia are 

 especially adapted as a resting stage, they contain a supply of 

 reserve material and may remain dormant for a considerable 

 period ; when, however, subjected to favourable conditions they 

 may germinate, protruding a number of tufts of fungus-threads 

 bearing conidia as before. 



The sclerotia have also another method of germination, instead 

 of producing conidia a short stalk is protruded, which expands 

 at its extremity into a small cup. The inner surface of this cup 

 is lined with a number of elongated special cells, termed asci, in 

 the interior of each of which eight small cells are developed 

 (ascospores). These cup-like structures with asci are common 

 (some attaining a diameter of two to three inches), and are 

 characteristic of a group of fungi known as Pezizas. The asco- 

 spores on germination may produce a new fungus. This we 

 may term the Peziza-stage. 



The above is a brief account of the complete life-history of 

 these fungi, it must, however, be noted that the full cycle has 

 not been established for all ; some, for instance, are only known 

 in the conidial stage, and others only in the peziza-stage. The 

 Pezizas are only developed upon the sclerotia, but the exact 

 conditions under which a sclerotium produces conidia or Pezizas 

 are at present undetermined.* 



The particular formf we have now under investigation pro- 

 ceeds to the development of conidia and sclerotia, but at present 

 I have not found any trace of a peziza-stage. 



* Miinter considers that some sclerotia require a rest of l^ears before producing 

 the Feziza. 



t In the Botanische Zeitung, 1886, de Bary published the result of his investigations 

 upon Sclerotinia (Peziza) sclerutiorum, a parasite upon various roots and tubers 

 when stored in cellars during winter, and also upon various seedlings— Zinnia, 

 Petunia, &c. He gives an account of the mode of life of the parasite, including the 

 conditions under which the plants are infected and the manner in which their tissues 

 are destroyed. 



In the Annals of Botany, Vol. II., we are indebted to Professor Marshall Ward 



