J 9°S^ Journal of the Mitchell Society. 67 



if it verge upon congestion of population, exacts an inevita- 

 ble forfeiture by increased mortality. Thus does the list of 

 diseases that conies within the horizon of the practical men 

 enlarge. Wonder, often scepticism, is expressed at the exist- 

 ence of unfamiliar diseases of man, other animals and plants, 

 as though these afflictions were conjured up by the examina- 

 tion of the over zealous practitioner. The increase of afflic- 

 tion is more apparent than real, as it is in the case of appen- 

 dicitis, which is now recognized, named and cured, conse- 

 quently, heard of, whereas under the old regime it was not 

 recognized as a distinct disease, therefore it was unheard of, 

 though the patient died. Parallel cases might be cited 

 among the plants. 



The work of DeBary on polymorphism among the fungi is 

 being extended. Knowledge of the life histories of various 

 pathogenic fungi is being slowly expanded. Summer forms 

 are connected with winter forms, and thereby the hibernating 

 condition, often the most vulnerable point of attack, exposed. 

 The discovery of heteroecism in the rusts, the alternation 

 from wheat to barberry, from apple to juniper is of classic 

 antiquity in the annals of plant pathology. It emphasized 

 the need of close study of life histories of all parasites. Such 

 studv has given abundant fruit, notably in disclosing the 

 relation between the apple cankers and the bitter rot of the 

 apple, and revealing the winter condition of the brown rot of 

 the peach. The lead so fortunately made in the discovery of 

 the Bordeaux mixture has been assiduously prosecuted. The 

 original Bordeaux mixture has been greatly modified, 

 changed, indeed, from a thick paste to a thin solution, and so 

 thoroughly tested in all its modifications, that it has now 

 reached its ultimate perfection. Hundreds of other chemi- 

 cals, both dry and wet, have been tested as fungicides, with 

 the adoption of a few adapted to special conditions, e. g:, sul- 

 phur and sulphides for powdery mildews and the ammoniacal 

 copper carbonate for use as the fruit ripens, thus avoiding 

 unsightly spotting. A happy combination of insecticide and 



