Cakxe — Brown Rot of Citrus. 
35 
All tlivoe species develo]) conidia en ])Otato dextrose agar. F. 
clirophtiiora has given the strongest vegetative growth on all the 
above media. P. hihcrnalis comes next except on .Fremdi beau agar 
on Avhich it makes ])oorer growth than P. ierresiris. 
As already stated P. hihenuiUs belongs to the Phasrolu group of 
Phytophthora as defined by Kosenliaum. He also points oat (25) 
that one of the most important and constant factors available for 
the distinction of species is the ratio between the mean length and 
the mean breadth of the conidia. Extending Rosenbaum’s table 
to include all the species noted in the literature available to the 
writer which would apt>ear to belong to the Phascoli group, the 
following table is proposed as a skeleton key to the species: — 
PHYTOPHTHORA-PHASEOLI GROUP. 
Majority bf antheridia amphigynous. 
1. Mean ratio of length of conidia to breadth 1.75 or less: — • 
P . melofjcna, Sawa<la 
1.2 
(17) 
P. parasitica, var, rliei^ Godfre 
*y 
1.32 
(17) 
P. aPH^ Sawada. 
1 . 35 
(17) 
P. (errestris^ Rherb. 
1 . 39 
(28) 
P. phascoli^ Thax. 
1.40 
(25) 
P. infestans (!Mont.) de Bary 
1.45 
(25) 
P. cryptofjaea^ Peth. & Laff. 
1.48 
(22) 
P. faberi^ Maubl. 
1 . 53 
(25 & 23) 
2^ . crythroseptica, Peth . 
1.57 
(25) 
P. arccae^ Colini. 
1 . 59 
(25) 
2. ^lean ratio greater than 1.75 
and 
less than 2: — 
P. parasitica^ Hast. 
3. Mean ratio — 2 or greater: — 
Conidia without persistent pedicels 
1.82 
(25 & 11) 
. mexicana Hot. & Hartge. 
up 
to 2 
(18) 
P. Meadii, McRae 
2 
(19) 
Conidia with persistent pedicels: — 
P. colocasiae, Rac. 
P. hibornaUs. Came 
2.2 
2.3 
(5) 
In \P. colocasiae the persistent pedicel is only occasional, and 
when present is less than half the length of the conidiuin. The 
conidia are larger and oospores smaller than in P. hihernalis. P. 
colocasiae is further distinguished by the presence of a cellulose 
plug at the point of insertion of the conidiophore into the conidiuin, 
and by the presence! of clilamydospores. 
