ROYAL BOTANIC GARDENS, KEW. 



BULLETIN 



OF 



MISCELLANEOUS INFORMATION. 



P * 



No. 7.] 



[1908. 







XXXVII -" DIE-BACK " OP PEACH SHOOTS. 



G. Massee. 



About 58,000 species of fungi have been described, and of 

 this number at least 10,000 are placed by mycologists under the 

 heading " Fungi imperfecti," on the assumption that such are in 

 reality nothing more than stages in the life-cycle of species of the 

 higher fungi, belonging to the Phycomycetes, Ascomycetes, and 

 Basidiomycetes respectively. This line of reasoning is supported 

 by the fact that in many instances such relationship has, by 

 means of pure cultures, been proved to exist. There remain, 

 however, many thousands of these forms that have not yet been 

 connected with any of the higher species, and as it is important 

 both from a scientific and economic standpoint that such should 

 be accurately described, they are grouped under " form-genera 

 and " form-species," thus implying that they are stages wnicfc 

 have not as yet been connected with higher species. 



Such form-species or conidial stages are unknown in connection 

 with the primitive species of aquatic fungi, and were only evolved 

 as supplementary stages when the fungi passed from their original 

 aquatic habitat and established themselves on dry land, inese 

 conidial stages possess many features in common, lhey are all 

 asexual in origin. The conidia are produced in immense numbers 

 and in rapid succession throughout that portion of the season 

 when the host of the fungus is in active growth The conidia 

 germinate at once when mature, and being dispersed wholesale by 

 wind, birds, insects, &c, are constantly infecting new hosts. JJj 

 fact, the special function of conidia is to extend he geographical 

 area of the species, while the spores of the original or higher ^ioim 

 of the species, which require a period of rest before they .are 

 capable of germinating, are only concerned with the surviva 

 of the species in time, by tiding it over that period when the host 

 ie not in a condition to furnish food for the fungus. 



From the above account it will be seen that the conidial form 

 of a fungus is invariably the cause of an epidemic i or of a apm 

 spread of a disease, except in those instances where ever ^ ^ nu,th o 

 has been superseded b/the presence of hybernating mycelium in 



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