Aug; zip 1923 
Phytophthora Faberi on Coconut and Cacao 
275 
MORPHOLOGICAL CHARACTERISTICS 
A comparative study from a morphological standpoint was made of 
both strains. Since no marked differences could be determined, one 
description only will be given to represent both. The descriptions of 
the morphological characters given before for the coconut strain by the 
writer (7) will be followed, but certain additional studies will be included. 
mycelium 
The mycelium is white, producing a dense mass in pure culture. It 
contains many nuclei. In young cultures it is nonseptate and granular. 
In older ones septa may be produced during spore production. Pro¬ 
toplasmic streaming is common. The submerged mycelium (PI. 9, A 
and B) is more or less gnarled, while the aerial is straight. Branching is 
abundant. The width varies from about 3 to about 8 ju. In the host 
tissue the mycelium is intercellular (PI. 8, A). Numerous fingerlike 
forms of haustoria are produced, penetrating the host cells (PI. 8, B). 
A distinct constriction is formed at the point of entrance into the cell. 
No cacao material was available at the time that the haustoria studies 
were made, so it cannot be stated with certainty that they are present in 
this strain. The similarity of both strains of the fungus in all other 
respects would lead one to believe that haustoria are also produced 
by the mycelium and present in the tissues of the cacao. 
CONIDIOPHORES 
Conidiophores are produced in great abundance in pure culture. 
Special culture methods must be employed to show them in their best 
condition. Material showing excellent conidiophore production may 
be obtained in sterilized Van Tieghem cells, by placing a few spores on a 
film of plain agar that has been spread over the flamed cover slip. Each 
conidiophore may bear from 1 to 15 or more conidia. A conidium is 
produced at the tip of a conidiophore; the latter then continues its 
growth by pushing the conidium to one side and produces another 
conidium at its tip. By a continuation of this process a bunch of spores 
is finally formed (PI. 9, C and D). The conidiophores vary in size, 
ranging approximately from 180 to 645 jjl in length, and from 3 to 6 n in 
width. 
CONIDIA 
The conidia are produced terminally as described above. They are 
elliptical to ovate, and possess very prominent, raised, terminal papillae 
(PI. 8, F and G; pi. 10, A and B). A short stalk may be present. The 
spores are pale yellow to colorless, are densely granular, contain many 
nuclei, and usually have a large vacuole (PI. 12, A and B). The nuclei 
are clearly shown in prepared sections stained by means of the triple 
stain (PI. 8, D, F, G). Older conidia usually possess more granules that 
are in groups. 
Measurements of conidia .—The measurements conform closely to 
those of Phytophthora faberi Maubl., using the methods employed by 
Rosenbaum ( 8 ). Measurements were made from oatmeal agar cultures. 
The coconut culture was 9 to 11 days old, and that of cacao 16 to 19 days 
old. The lengths and widths of 400 spores were measured. The results 
are presented in Table I, which gives the class in microns and the number 
of conidia out of 400, both for length and width, that falls into each class. 
