182 Parasitic Aphelenchi 
through the kindness of Sir David Prain and Mr Arthur Hill, and (3) Chrysan¬ 
themum leaves containing the new species A. phyllophagus , from Messrs Tacon 
and Horwood, Cheshunt, Hertfordshire. 
Regarding this disease in chrysanthemums, Messrs Tacon and Horwood 
write, that they have had this trouble for ten years at least; in one batch of 
pot chrysanthemums (Cheshunt White) one half were affected; they have 
been compelled to abandon certain varieties entirely, as they used to lose all 
their leaves. 
Strawberry bunch and Aphelenchus leaf disease are therefore two wide¬ 
spread and destructive plant diseases, which cause considerable loss to the 
growers of fruit and flowers. 
III. SPECIFIC DISTINCTNESS OF APHELENCHUS FRAGARIAE R.B., 
A. OLESISTUS R.B., AND A. PHYLLOPHAGUS N.SP. 
A. fragariae and olesistus. Ritzema Bos distinguished his two species by 
their pathological effects on their hosts. Several points of anatomical distinc¬ 
tion must have been observed under low powers of the microscope, but they 
are unsatisfactory. The tail of A.fragariae narrows suddenly behind the anus, 
that of A. olesistus does not. 
Marcinowski (1908) considers A. fragariae identical with A. olesistus , and 
possibly also with A. helophilus De Man. The differences in measurements 
she considers to be within the limits of individual variability. She performed 
experiments which she claims prove that the Aphelenchi of orchids and 
begonias can be transferred to strawberry plants. 
Infected orchid leaves were placed in contact with (1) begonias, (2) strawberry plants. 
In (1) immediate infection occurred with typical leaf disease; in (2) on the other hand no 
Aphelenchi were found on the strawberry plants during the first month, thereafter only a 
few in one plant; leaf disease and not characteristic strawberry bunch resulted. 
This experiment therefore so far from proving the identity of A. olesistus 
and fragariae tends to prove their distinctness. 
A. phyllophagus . When numerous fresh and well-mounted specimens are 
compared with A. fragariae and olesistus the following differences are obvious: 
it is a larger and more robust animal, and the excretory pore is situated some 
distance behind the nerve ring, while in A. fragariae and olesistus it is on a 
level with the nerve ring. 
The difference in size between A. phyllophagus and A. olesistus is not a 
mere temporary difference between individuals of the same species due to 
the occupation of different host plants. I transferred both species to cabbage 
seedlings, but they retained their differences of size in the new host. It should 
be noted that the stomata (through which the parasites enter the plants, 
vide p. 176, E) are larger in the normal hosts of A. phyllophagus (chrysan¬ 
themums) than in the normal hosts of A. olesistus (begonias and ferns). The 
two species are therefore adapted to their normal hosts. 
