[ 29 ] 



No. 4. 



ON A PHYTOPHTHOEA PARASITIC ON APPLES WHICH HAS BOTH 

 AMPHIGYNOUS AND PAEAGYNOUS ANTHEEIDIA; AND ON ALLIED 

 SPECIES WHICH SHOW THE SAME PHENOMENON. 



By H. A. LAFFEETY 



AND 



GEOEGE H. PETHYBEIDGE, 



Seeds and Plant Disease Division, Department of Agricultuie and Technical 



Instruction for Ireland. 



(Plates I and II.) 



[EeadMAY23. Printed June 28, 1922.] 



The work described in the present paper originated from an examination of a couple 

 of apples of the variety "Lane's Prince Albert," which were affected with an 

 unusual form of rot, and were submitted for report in November, 1920, by Mr. E. 

 Turner, one of the Department's Horticultural Inspectors, from Pilltown, County 

 Kilkenny. The diseased fruits were apparently healthy when gathered on 

 October 14th as portion of a lot specially selected for exhibition purposes, and 

 they began to rot about ten days later. Whether infection occurred prior to 

 gathering or during storage is not known. 



1.— Nature of the Rot. 



The decayed apples had dark brown skins, but they were more or less firm and 

 elastic to the touch. They showed no signs of superficial wounds, nor were any 

 external indications of fungus growth visible on them. After they had been kept 

 under a bell-jar in the laboratory for a few days, however, small white tufts of 

 hyphae were present at some of the lenticels. These proved to be composed 

 of non-septate mycelium, which was almost entirely sterile ; but prolonged search 

 ultimately resulted in the discovery of two sporangia, suggestive of a Phytophthora. 



Further examination, made at a later date, revealed the presence of a few 

 sexual organs, borne on the mycelium in the basal portions of several of the tufts. 

 The oogonia averaged 26-'i/,t and the oospores 24'4|U in diameter. The surprising 

 thing about the sexual organs was that they were of two types. In the majority 

 of eases the antheridia were lateral' {paragynous), but in a few instances they were 

 observed to be of the type first discovered in Pliytophthora erytliroseptica, i.e., sur- 

 rounding the base of the oogonium (amphigynous).- 



The tiesh of the diseased apples was brown in colour, fairly firm, and not pulpy. 



' Not necessarily lateral in the strict sense of the word, because such antheridia are frequently 

 situated more or less below or at the base of the oogonium near the stalk, but not surrounding 

 or penetrated by the latter. 



-The convenient terms, " amphigynous" and " paragynous," for expressing the position of 

 the antheridium in relation to the oogonium, were suggested by P. A. Murphy, Ann. Bot. , xxxii, 

 1918, p. 125. 



SCIENI. PBGC. E.D.S., VOL. XVII, NO. i. H 



