362 Wormald. — ‘ Brown Rot ' Diseases of Fruit Trees. 
The most important of the fungi producing these symptoms are to be 
referred to that genus of the ‘Fungi Imperfecti ’ known as Monilia. 
Although these Monilias are able to continue from year to year without 
the interpolation of an ascigerous stage, such a stage has been observed, 
and it is now customary to allocate the species to the ascomycetous genus 
Sclerotinia . 
The effect produced on the fruit by these species of Monilia is 
commonly known as ‘ Brown Rot ’ in this country, and this term is also 
now generally applied to the various diseases of fruit trees caused by 
these fungi. On the Continent the same diseases are referred to as ‘ Rot 
brun ‘ Faulniss der Friichte’, ‘ Grind oder Schimmel des Obstes ’, ‘ Schwarz- 
faule ’, ‘ Bluten- und Zweigdiirre ’, ‘ Muffa o marciume dei frutti ’, &c. The 
result of the development of the Monilias within the tissues is not usually, 
however, a ‘ rot ’ in the sense of putrefaction, since the organs attacked 
become so permeated with the mycelium that the whole forms a stromatic 
mass which generally tends to become more or less indurated rather than 
rotten. Thus the fruit, when so infected, instead of decaying and disin- 
tegrating, often becomes desiccated, and may remain on the tree in a 
‘ mummified ’ condition for some months. 
Towards the end of the nineteenth century serious losses to the cherry 
crops on the Continent, the flowers, fruit, and often branches being killed, 
led to an investigation of the cause of the outbreaks. The disease, at first 
attributed to the action of frost, was soon found to be due to epidemic 
attacks of a Monilia. It is now generally recognized that although the 
Brown Rot fungi are usually associated with fruit-rots they also cause 
blossom-wilts, destroy young twigs, and often kill branches by producing 
cankers which, girdling them and penetrating to the xylem elements, 
obstruct the course of the transpiration current and so cause the desiccation 
and death of those parts distal to the cankers. 
The fruit is also liable to infection after it is picked, and apples in the 
store often suffer severely, for, since the disease under certain conditions is 
contagious, one affected apple may transmit the rot to those around it. 
Under storage conditions apples attacked by M. fructigena sometimes 
become quite black, a fact recorded in this country as early as 1885 by 
Worthington G. Smith. 
That the Brown Rot fungi are recognized by mycologists and phyto- 
pathologists as of paramount importance is shown by the numerous papers 
and articles which have been published on the subject. 1 Many of these 
articles are merely records of the occurrence of the? diseases, and relatively 
few supply scientific evidence for the conclusions arrived at. Of the 
experimental work, particularly that carried out on the Continent, very few 
investigators employed ‘ pure culture’ methods in carrying out inoculations, 
1 See Bibliography on pp. 398-403. 
