Oakxe — Brincn Rot of Citrus. 
2 \) 
(24). T)ie oog'oiiial wall takes on the same colour and ])ersists 
a rather irre<>'ular rough coating to the oos]>ores. 
The Phytophthora causing rotting of citrus fruits in Portugal 
deseribed by Moniz da Maia (20) agrees so closely Avith P. hihrr >■ 
a!is that there is no doubt that they are identical. The former has 
})een isolated from the orange, mandarin and lemon fruits. The 
conidui are formed in similar manner to 2\ itihcrnaJis, and are 
similarly eharacterised by tlieir elongate form and the ])resence of 
persistent pedicels. Moniz da Maia, however, recognises macro-coiiidia 
on fruit measuring 17. d — d8mmm. x 7.d — Idmmni., and micro couidi i 
on cultures measuring dO — d7.dmmm. x 10 — 18.5mnim. lu the w-uk 
done (Ui 7\ hibcnuCis the author has found no definite distinction 
between the larger and smaller conidiUj and regards them as sim])ly 
indicating the range of variation, and perhaj)S in the case of tie* 
smaller as evidence of immaturity. As already shown conidia ('oni- 
])arable with Moniz da Maia’s largest and smallest have been ol->- 
taine-d from cultures of P. hihcniaUs . 
( nlv 0-10 zoos]>ores have been noted in Moniz da iMaia’s cid 
tures but he has admittedly observed only a very few cases of 
zo()S]K>re formation. He gives 22 to 42.dmmm. as the measuremenl- 
of the iKis])ores, wliielr coni])ares favoural)ly Avith 22 to 4d.(immm. in 
J\ hihrrtuiUs. ^‘This disease ap]>ears in mid-winter (January), and 
causes damage in the early spring, covering a ])criod of niarkedlv 
low temperature, and generally associated Avith rain, snow ami 
fi'ost. This agrees absolute'}’ in seasonal occurrence with P. };ihrni- 
alis. The microphotograi>hs j)ublished of mycelium, conidia, and 
oogonia also agia-e A’ery closely Avith I\ JiibcnxiHs . 
INFECTION ENPERIMENTE. 
In 1923 infection was secured of tAvo oranges with spores ])io- 
duced in Avater cultures from brown-rotted oranges. Tin* sus})ensiiui 
of the spores in Avater was placed in glass rings fastened to the 
fruits with jdasticine, and coA’ored AvitJi glass slips sealed wbli 
A’aseline. The ])ositive results Avere obtained Avith scratched fruit 
only . 
Culture J. 
9/1 0/2,'’- -Hnseratched Scratched 
l(>/10/2b-:— — d- 
24/10/2:1 — + 
Co/itrol. 
9/10/23 — -Fnscratched 
16/10/23 — 
24/10/23 — 
Culture B. 
T^nscratched Scratched 
+ 
+ 
Scratched 
In 1924 many attempts were made to infect fruits ]>y j)lacing 
tliem in contact Avith affecUnl fruits, or in Avater containing affected 
fruits, or in Avhich the vSame had been placed for several days. In 
