W or maid, — ‘ Brown Rot ’ Diseases of Fruit Trees . II. 165 
which have been obtained from plums and cherries have always produced 
conidia freely on potato. 
This difference in the conidial productivity of the two forms of 
M. cinerea has been noted also in the case of cultures growing on starch 
jelly prepared with the ‘ Modified Uschinsky’s Solution ’ as recommended by 
Erwin Smith ( 24 ) for bacteria. Up to the present only two strains of each 
form have been cultivated on this medium in comparative tests. The two 
plum strains produced numerous conidia, but none could, be found in the 
cultures of the two apple strains. 
Cultural methods have also shown that there is a difference even in the 
mode of germination of the conidia when these are placed on prune juice 
agar. Typically the germ tube of M. fructigena grows out as a single hypha, 
almost straight, for some 400 to 1,200 /ot before it branches to form a den- 
dritic branching system terminal to the primary germ tube, within from 24 
to 48 hours at room temperature ; often a very short germ tube 10 to 30 \i 
in length develops at the opposite end of the conidium. The germ tube of 
M. cinerea , on the other hand, usually becomes geniculate and soon produces 
branches at a short distance from its point of origin, so that the branch 
system is very irregular from the first. In both species the hyphae, after 
48 hours, grow out in all directions to form a more or less circular disc of 
mycelium. 
When growing on agar culture media both M . fructigena and M. cinerea 
(including the American form of Monilia ) produce numerous clusters of 
minute ‘ microconidia ’ or ‘ sporidia \ These spore-like bodies are globose 
and about 3 /x in diameter ; attempts to induce them to germinate failed. 
That cultural and biochemical methods employed in the laboratory will 
prove of service in distinguishing between morphologically similar forms of 
fungi is becoming more and more evident. Such methods are indispensable 
to the bacteriologist, and they offer to the mycologist a wide and interesting 
field for study. Alsberg and Black ( 2 ) found that biochemical methods were 
useful in identifying species of Penicillium which are not easily distinguished 
morphologically, and Grossenbacher and Duggar ( 12 ) were able to distin- 
guish parasitic and saprophytic strains of Botryosphaeria ribis by means of 
artificially prepared cultures. 
(e) American S trains of Monilia. 
Until a few years ago plant pathologists in North America had attributed 
Brown Rot diseases in that continent to Monilia fructigena. Recent writers, 
however, conclude that it is identical with Monilia cinerea , Bon. : thus 
Bartram ( 3 ) writes : ‘ The common form of brown rot of stone fruits, as found 
in Vermont, is due to the fungus known in Europe as Sclerotinia cinerea. 
This is conclusively proved not only by the measurements of the conidia, 
the absence of disjunctors, the grey colour of the conidial tufts, but more 
