69 



the normal manner on the leaves. They had less colour, and were 

 somewhat smaller. It was in part upon this evidence that the fungus 

 was assigned to the group Alternaria. 



As an example of the occurrence of the disease on citrus fruit, it 

 may be mentioned that on one occasion three mandarins of the variety 

 "Emperor" were examined, each with a single well-marked spot, 

 at which the fungus had injured the skin and caused an unsightly 

 blotch. 



The mandarins were green, but would soon have ripened. The 

 location of the diseased areas was marked by a premature <( ripening," 

 the diseased spots being surrounded by a yellow area, which shaded 

 off into the normal green of the fruit. At the centre of the spot the 

 tissues had been almost completely destroyed nearly down to the pulp. 

 The original succulency of the tissues was completely gone. The tissue 

 of cells composing the rind had been used up by the parasite, and in 

 their place was a cracked and dried-up mass largely composed of the 

 mycelium and spores of the fungus. 



With a knife-blade it was easy to break away the brittle mass of 

 diseased material, which might, therefore, perhaps be called scabby in 

 its nature, though the growth was somewhat sunken, not raised. 

 This scabby material was lig-ht gray or ash-coloured, except at the 

 surface, where, owing to the presence of the fungi, the colour was 

 darker dark-green or nearly black. The diseased spots measured 

 about five millimetres across that is to say, not far from a quarter of 

 an inch. Two fungus forms were found on and in the diseased 

 tissue, an Alternaria and a Phoma. 



An exceptionally wide cell gave 58 x 21 /x. It may be said that the 

 mature spores having six to twenty cells measured 1422 x 36 65/x. 

 Taking the complete range of spores in the two cases, i.e., the orange 

 leaf and the mandarin fruit, we have the following comparison : 



On Orange Leaf, 10-18 x 15-75, 

 On Mandarins, 7-22 x 11-65, 



in which we see a practical identity. The form, colour, and structure 

 were as nearly as possible identical in the two cases. In the case of 

 the mandarin, however, the spores were not seen growing tandem. 

 That method is assumed on the ground of complete general resemblance. 

 The curved or crooked pedicels on which the spores were borne were 

 two to five celled, and measured 44-90 /u, x 4'7-5'6 ^. The locations of 

 the septa were indicated by slight irregularities in the exterior of the 

 hypha. These pedicels grew in tufts of five to ten, and were readily 

 to be seen with a good hand lens. Both the pedicels and their spores 

 were of a greenish- brown colour, except the terminal cell of the spore, 

 which was nearly colourless. 



