98 ^1 Pln/to2)]ithora Rot of Peavii and Appleii 



The Rot on Apples. 



In the summer of 1915 two apples affected with a soft rot were 

 received from Surrey, the diseased areas showing, where the skin was 

 ruptured and turned back, a white "bloom" which proved to be my- 

 celium ; a few sporangia of the Phytojihthora type were obtained from one 

 of the apples. Later other specimens were obtained from the same 

 source: they were all of one variety of apple, viz. Lane's Prince Albert. 

 The majority of these again showed the white film of mycehum where 

 the flesh was exposed. One of them had no trace of any fungus on the 

 surface although nearly half the apple was soft and brown ; the diseased 

 tissues however contained rather coarse, guttulate, non-septate hyphae, 

 and particles of the flesh, cut out with a sterilized razor and placed on 

 agar developed into cultures similar to those obtained from the Fhytoph- 

 thora on pears. 



The white " bloom " was seen only on those apples where the skin had 

 become torn and had rolled back exposing the flesh underneath; this 

 condition obtained in most of the apples examined (see Plate III. fig. 3). 

 In those where the skin was intact the mycelium was either not apparent 

 at the surface or it issued through the skin as small tufts of hyphae 

 which were quite barren, neither sporangia nor sexual organs being 

 found on them. 



Sporangia occurred far less frequently on these apples than on pears 

 infected with the disease; of the 14 affected apples examined sporangia 

 were found on four only at the time they were received. Osterwalder(4) 

 found that such apples could be induced to develop PJii/fophfhora 

 sporangia freely by immersion in water, so one of the apples on which 

 no sporangia could be found was immersed in a beaker of water which 

 was then covered with a bell-jar. Within 24 hours a white weft of my- 

 celium had grown out into the water; on placing a little of this mycelium 

 on a slide numerous sporangia were seen and on adding a little distilled 

 water numerous zoospores were liberated within two hours. 



In 1917 two apples showing a similar rot, no reproductive bodies 

 being present, were received from Sussex; the tissues however were 

 permeated with mycelium which grew out readily when particles of the 

 flesh were placed on agar. The resulting cultures developed sexual 

 organs similar to those found in the other cultures. 



Inoculation Experiment 7. Apples and pears were inoculated simul- 

 taneously with two strains of the fungus, one isolated from an apple, 

 the other from a pear. The two strains gave identical results; no spor- 



