Mar. 1, 1925 
PTiytopTithora Rot of Pears and Apples 
467 
Antheridia are usually paragynous 
(pi. 2, C and D) but in old cultures on 
oatmeal paste a few have been found 
which were amphigynous (pi. 2, E, F, 
G, and H). Lafferty and Pethybridge 
(6, p ; 36) have already reported this 
condition for cultures of Phytophthora 
cactorum obtained by them from 
various sources, including one fur¬ 
nished by H. H. Whetzel and said by 
him to have been isolated from a 
decayed apple grown in his own garden 
in Ithaca, N. Y. Rose (10) has also 
reported it for a Phytophthora isolated 
from decaying strawberries and shown 
by him to be very similar to Phytoph¬ 
thora cactorum. The writers wish to 
call attention, however, to an unusual 
form with two amphigynous antheridia 
shown in Plate 2, H. As seen under 
the microscope, the antheridia lay in 
approximately the same plane." It 
was thought at first that there were 
two oogonia, one lying over the other; 
but after repeated and vigorous tap¬ 
ping of the cover glass the object still 
remained as figured on Plate 2, one 
oogonium with two amphigynous an¬ 
theridia. 
The oogonium is apparently intercal¬ 
ary, but even so it is difficult to under¬ 
stand how it could have grown through 
two antheridia in the manner described 
by Pethybridge (9) for growth through 
one. In other words, the finding of 
the form here under discussion (pi, 2, 
H) raises the question whether for the 
apple and pear Phytophthora an¬ 
theridia in the amphigynous position 
have that position because the oogon¬ 
ium has grown through them. The 
writers have no other explanation of 
how antheridia iryiy become amphi¬ 
gynous but will merely add that at no 
time during a rather extensive study 
of the apple and pear Phytophthora 
have they seen early stages of the 
growth of the oogonium through the 
antheridium. Antheridia in the am¬ 
phigynous position have been seen 
only in the final, fully developed 
stage and only in old cultures or in 
the older portions of cultures that 
were a month to six weeks old. 
It should be added that an oogonium 
with two amphigynous antheridia has 
been seen only once. Attention is 
called, however, to Plate 2, D and E, 
which shows two oogonia, each with 
one amphigynous and one paragynous 
antheridium. One of these aggre¬ 
gates lay in an open space between two 
masses of mycelium and was made to 
assume different positions by pressure 
on the cover glass. Study of it in 
these positions showed that the struc¬ 
tures figured in Plate 2, D, were not 
merely in fortuitous juxtaposition but 
were actually parts of one whole. 
The other (pi. 2, E) lay in a matrix of 
agar and mycelium and was studied 
only in the position shown by the 
drawing. It would be possible of 
course for one antheridium to assume 
a position at the side of an oogonium 
after the latter had grown through 
another antheridium. The figures are 
included here merely on the chance 
that they may at some time help to 
explain the condition shown in Plate 2, 
DISCUSSION 
The finding of Phytophthora rot 
on fruits on the Chicago market is a 
new record, so far as the pathological 
work is concerned which is carried on 
in connection with the Food Products 
Inspection Service. That is, the rot 
has not heretofore been seen in the 
course of this work, or, if seen, has 
not been recognized. The finding 
of the rot on pears and apples from 
Michigan and on apples from Washing¬ 
ton and Idaho is, so far as the writers 
are aware, a new record for each of 
those States, though not for the con¬ 
tinent of North America. Whetzel and 
Rosenbaum (15) reported Phytophthora 
cactorum from New York on Duchess 
apples in 1916, Hesler (14, P . 172) 
from New York on apples in 1918, 
Gtissow (4) from Canada on pears in 
1919, Clinton ( 3, p. 454) from Con¬ 
necticut on pears in 1919 and on 
apples in 1920 (3, p. 406), and Gardner 
(5, p. 53) from Indiana on apples in 
1921. Phytophthora cactorum is a well- 
known parasite of pears and apples in 
Europe (Wormald, (16), Osterwalder 
(8), Lafferty and Pethybridge (6) 
EXPLANATORY LEGEND FOR PLATE 2 
Spore forms and sporophore of the Phytophthor isolated from apples and pears. (A, B, C, 
D, E, F, G, H, L X 785. J, K, I, M X 369) 
A, B.—Conidia 
C. —Oogonium with paragynous antheridium 
D, E.—Oogonia, each with one paragynous and one amphigynous antheridium 
F, G.—Oogonia, each with one amphigynous antheridium 
H, —Oogonium with two amphigynous antheridia 
I, J, K, L.—Various forms of Sphaero-conidia 
M.—Conidiophore with conidia attached. Lower portion of the figure shows manner of origin 
from the mycelium 
