M. C. COOKE ON MICROSCOPIC MOULDS. 



63 



the naked eye that the microscope must be resorted to for their 

 determination. In all these species the flocci are dark, erect, and 

 either simple or slightly branched, bearing here and there multisep- 

 tate spores. In such a species as Helminthosporium Tilice the 

 threads themselves seem to enlarge and develope into spores. In 

 some the spores are deeply coloured, in others they are nearly 

 colourless. Near two dozen distinct species have been recognised 

 in this country, and a few more workers would soon increase the 

 number.* It is sometimes objected that the species of fungi are im- 

 aginary. Let those which constitute the present genus be examined 

 carefully, and it will soon be discovered that the objection had its 

 foundation in ignorance. There must first of all be an apprecia- 

 tion of what constitutes a specific difference in fungi before it 

 can be maintained that there are no good species. It is admitted 

 that only a trifling difference in one or more organs, if compara- 

 tively permanent, is enough to constitute a good botanical species. 

 I am content to give up at once any one or more of the British 

 species of Helminthosporium, for instance, if it can be shown that 

 what are accepted as the specific distinctions are not permanent, in 

 the sense that permanence is accepted amongst flowering plants. 

 Indeed I incline to the opinion that variability within the limits 

 of a species is less than in the higher plants. The more ex- 

 perience one acquires the more firm becomes the conviction that 

 the general principles of classification in fungi are sound. Of 

 course this does not affect, and is not affected by the autonomy 

 of species. The evidence that a certain form is only a stylosporous 

 condition of an ascigerous species, does not prove that the stylo- 

 sporous condition is not of itself permanent in its stylosporous 

 character. It is a favourite theme with some who know little, 

 and care less, about fungi, to indicate the proven instances of 

 dimorphism, and jump at once to the conclusion that the study 

 is altogether a chaos, and that there are very few, if any, good 

 species at all. Because what has been known as Tubercularia 

 vulgaris is now proved to be a conidiiferous condition of Nectria 

 cinnabarina, that does not prove that Tubercularia vulgaris is in 

 itself so variable that no reliance can be placed on other species 

 of the same genus, or that the conidia were not sufficiently per- 



* Anew species was figured and described in the " Gardeners' Chronicle" 

 of March 19th, under the name of Helminthosporium echinulatum, which is re- 

 markable for its echinulate spores, all previously known species having the 

 epispore smooth. 



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