The Morphology and Cytology of the Sexual Organs 
of Phytophthora erythroseptica, Pethyb. 
BY 
PAUL A. MURPHY, B.A., A.R.CSc.L, 
Late Development Commission Scholar in Plant Pathology. 
With Plates II and III. 
Contents. 
PAGE 
Introduction.115 
Technique . . . . . „ 116 
Development of the Sexual Organs : 
Penetration of the antheridium by the 
oogonial incept . . . .122 
Heterothallism . . . . .127 
Further growth of the sexual organs 
and degeneration of nuclei before 
division ..... 128 
Arrangement of the nuclei during 
division ..... 131 
PAGE 
Nuclear division . . . . 132 
The receptive papilla or manocyst . 134 
The oosphere and fertilization . .136 
The oospore . . . . .140 
General Considerations . . . 142 
Summary ..150 
Bibliography.151 
Explanation of Plates . . .152 
T HE description of a new species of Phytophthora , P. erythroseptica , by 
Pethybridge ( 27 ), of such an aberrant type that the author in ques¬ 
tion considered it necessary to divide the genus as established by de Bary 
into two, 1 and the subsequent discovery that several other species— 
P. Phaseoli (Pethybridge, 27 ), P. infestans (Pethybridge and Murphy, 80 ), 
P. parasitica (Dastur, 18 ), P. Colocasiae (Butler and Kulkarni, 7 ), and prob¬ 
ably P. Arecae (Pethybridge, 27 ; Coleman, 11 )—had the same type of 
sexual organs as P. erythroseptica , made it desirable to carry out a thorough 
1 Pethybridge ( 1 . c.) named the division of the original genus which has sexual organs of the 
same type as P. erythroseptica , Phytophthora because the type. species P. infestans belongs to it; 
for the other division, headed by P. Cactorum , he established the new genus Nozemia. Wilson 
(Studies in North American Peronosporales. V. A Review of the Genus Phytophthora. Mycol., 6, 
pp. 54-83, PL 2, 1914) has advanced reasons to show that the new genus should be called 
Phloeophthora (not 4 Phleophythora ’ as given by that author) because the Fungus Phytophthora 
Syringae had first been named by Klebahn from its sexual organs, which were found without 
mycelium, Phloeophthora Syringae. This reasoning seems to be based on a misapprehension as to 
the nature of a pleomorphic life cycle, and is open to grave question. The writer believes that he is 
following the International Rules (1910), which tacitly exclude the Phycomycetes from other Fungi 
as not possessing pleomorphic life cycles, and therefore adheres to Pethybridge’s nomenclature in this 
paper. 
[Annals of Botany, Vol. XXXII. No. CXXV. January, 1918.] 
