Apr. IS, 1918 A Leafblight of Kalmia latijolia 203 



INOCULATIONS INTO OTHER PLANTS 



The differences morphologically are not very great between the fungus 

 here under consideration and certain species of Phomopsis which cause 

 diseases of Citrus spp., eggplant, and apple. It was therefore thought 

 advisable to carry out cross-inoculations. 



Apple, orange, and lemon fruits and young, growing eggplants were 

 inoculated with the fungus isolated from K. latijolia. The fruits and 

 plants were kept under as favorable conditions for infection as possible, 

 and the virulence of the cultures used in each experiment was tested out 

 by inoculation into K. latijolia. 



No infections resulted from any of the inoculations. In the experiment 

 on apple bacterial sof trots appeared, and in one case a fruit showed a 

 spot just at the margin of one of the inoculation pricks which appeared 

 at first somewhat like the Phomopsis-rot of apple described by Roberts 

 {8, 9). Microscopic examination revealed very large, brown hyphae, and 

 cultures gave no colonies of the mountain-laurel fungus. 



Sufficient experiments were performed to indicate that the species of 

 Phomopsis here described is not the same as Phomopsis citri Fawcett (6) 

 which causes melanose and stem endrot of Citrus fruits (4, 7). In addi- 

 tion to its inability to infect Citrus fruits, it differs morphologically from 

 the fungus described by Fawcett (4), in that the pycnidia are not em- 

 bedded deeply in the tissues of the host, and in no culture medium was 

 there formation of Achyla-like branches with protrusion of the proto- 

 plasm from the ends, such as Fawcett describes. 



It is not infectious to eggplant, and therefore not the same as Pho- 

 mopsis vexans Harter (10), from which it differs also in pycnidial char- 

 acters — for example, there is no beak either on the host or in culture 

 media. 



The negative results from the inoculations into apple distinguish it 

 from Phomopsis ma,li Roberts (9), though morphologically it is very 

 much like this species, with the exception that the spores are smaller, 

 and often contain more than two oil drops. 



EFFECT OF THE FUNGUS ON THE TISSUES 



Microscopic examination of sections fixed in Camoy's fluid and stained 

 by Van Gieson's method shows that the diseased areas consist of a 

 confused mass of disintegrated leaf tissue and mycelial cells. The fungus 

 is seen to extend not far beyond these diseased areas; and this, together 

 with the fact that the mycelium is extremely delicate and hyalin, makes 

 it rather difficult to locate in the host tissues. Very young spots, sec- 

 tioned horizontally and stained by special stains, such as Van Gieson's, 

 give best results. In such sections the fungus may be seen ramifying 

 through the intercellular spaces both in the palisade tissue and in the 

 spongy mesophyll. The chloroplasts are greatly reduced in number 

 for a considerable distance around the diseased area, and the nuclei 



