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larity to the form of the spores spores that under other conditions 

 would be symmetrical, becoming bent and clavate. With regard to 

 the colour of the spores, I am not so certain; but I have seen quite 

 perceptible changes of colour due, apparently, to the change of 

 host-plant in the course of a series of inoculations. For example, 

 I observed that the somewhat brightly-coloured spores of the Gloeo- 

 sporium of the guava became less brilliant after two or three genera- 

 tions on pomaceous fruits. 



All these various properties of the fungus should be considered to be 

 to a considerable extent a function of the host-plant, just as the size, 

 form, and colour of Phaenogamous plants are to a certain extent 

 functions of the soil and climate in which they are produced. 



If these ideas are correct, and my observations leave me no doubt 

 that they are at least approximately correct, they must cause us to 

 consider the size, form, and colour of spores in the light of their 

 origin, and not refer to them indiscriminately as characteristics of the 

 fungus, and make them the basis of descriptions of " species." 



Consider for a moment the colours called forth on these same host- 

 plants by other fungus diseases than the ripe-rot fungi. It is quite 

 evident from such an examination that each species of fruit has certain 

 ranges of colour in its rots, regardless to some extent of the exciting 

 cause. These colours are due to certain chemical changes in the 

 tissues of the fruit, and these changes are at bottom similar for quite 

 a range of injuries. Here again we see that the resulting compounds 

 and their colours are to a certain degree a function of the object 

 attacked, and we cannot logically refer them indiscriminately to the 

 attacking agency. 



While these statements may not be capable of being set down as 

 hard and fast laws, they embody too much truth to be so generally 

 ignored as they have been in the past, particularly by systematists. 



The facts strongly suggest that a considerable number of the 

 various so-called species of Gloeosporium, showing as they do when 

 grown on different fruits no greater variations than we expect to see 

 in various plants when grown on a variety of soils, are in reality too 

 closely related to require distinct names are in reality one and the 

 same form or species. 



Other recent observers have arrived at similar conclusions as the 

 result of more or less extensive experiment. 



The fact that the ripe-rot fungus of a given fruit can be grown on a 

 great variety of other fruits, and that it actually occurs in nature on a 

 great variety of other fruits, may appear capable of another inter- 

 pretation than that suggested by the foregoing paragraphs. It may 

 be argued that in spite of the close resemblances among the various 

 forms, there are as many species as there are kinds of fruit; that the 

 mere fact of each such form growing on other fruits is no proof that 

 it is not in itself a true species ; that there are other important 

 factors besides form, colour, size, and structure that enter into the 

 idea of a species, namely physiological adaptation to environment, 

 chemical composition, &c., and that these do not find expression in any 

 visible manner. 



