1 66 Wormald. — ‘ Brown Rot ’ Diseases of Fruit Trees. II. 
especially by the persistence of the vitality of the conidia through the 
winter.’ 
Ten strains of this American form have been received at Wye from 
three different localities in North America, viz. Wisconsin, Oregon, and 
Ontario, and from three different hosts, viz. apple, plum, and peach. They 
have been cultivated and examined side by side with cultures of the forms 
occurring in this country. It was found that the American Monilia could 
be distinguished in cultures from the forms of M. cinerea occurring in 
England, in the readiness with which it produces conidia, and in its mode of 
growth when cultivated on prune juice agar. 
The European form does not produce conidia 1 on prune juice agar or 
carrot agar, nor in such liquid media as fruit extracts or Coons’ solution, while 
the American strains develop numerous well-developed pustules on all these 
media. On prune juice agar the American form •grows out uniformly to the 
edge of the plate, and in this respect resembles M. fructigena rather than 
our native forms of M. cinerea ; these cultures, however, can easily be distin- 
guished from those of M. fructigena by the numerous small grey tufts of 
conidiophores which develop (Fig. 7). 
Again, in the mode of branching of the germ tube of the conidium, 
on agar plates, the American form of Monilia more nearly resembles 
M. fructigena than M. cinerea. The germ tube shows less tendency to 
become geniculate than is the case with that of M. cinerea ; it is usually at 
least 200 n in length before it begins to branch, and unbranched germ tubes 
650 and 750 n in length have been observed. 
(f) Taxonomy. 
The results of observations and experiments recorded in the present 
paper show that there are two distinct species of Monilia occurring in Britain, 
and that they are to be distinguished as follows : 
M. fructigena. 
Pustules. 
Dimensions of conidia. 
Mode of germination of coni- 
dia on prune juice agar. 
Cultures on prune juice agar 
plates. 
Winter condition. 
Buff yellow. 
Average about 2 1 x 1 3 /t. 
Typically produces a long germ 
tube, 600 to 1,200 /* in length, 
before branching. 
Growth uniform to edge of 
plate ; margin entire or sub- 
entire. 
Pustules generally barren in 
winter or bearing non-viable 
conidia. 
M. cinerea. 
Grey, generally smaller than 
those of M. fructigena. 
Approx, average. 
Winter conidia, 1 1.5 x 8 /*. 
Summer conidia, 17x11/*. 
Germ tube branches while still 
quite short, often close to its 
point of origin ; it is usually 
geniculate at one or more 
points. 
Growth zonate ; margin lobed. 
Pustules and conidia produced 
freely in winter. 
1 A few conidia tufts have been observed in one instance only when prune juice agar was used, 
in a tube culture of a plum strain which had been growing at a fairly low temperature (7°-i5° C.) 
for some weeks. 
