A. S. HoiiNK 187 



generally triHing."* Owing to the regnltitions adopted by other Govern- 

 ments, however, the indirect loss to potato-growers is very considerable. 

 The question of tiie degree of virulence possessed by this organism 

 needs searching analysis and the following points may be enumerated in 

 this connection : 



( 1 ) Tubers planted in experimentally infected soil have produced 

 without fail plants bearing diseased tubers (M. C. Potter). 



(2) Diseased tubers have been produced year after year, 

 irrespective of the kind of season, in soil once infected (M. C. 

 Potter). 



(3) Several varieties of potato were affected when planted in 

 Potter's experimentally infected soil. 



(1) The Report issued by the Intelligence Division, 1911-1912, 

 states that in spite of the exceptionally dry season in 1911, the disease 

 in all the badly affected places was as manifest as ever even though it 

 was not observed in the less badly attacked districts. 



(5) According to the Report, some varieties are practically 

 immune to Chrysophlyctis. 



It may be gathered from the Report that the disease is largely 

 confined to cottage and allotment gardens. Now in gardens of this 

 type, frequently ill-kept, where potatoes are grown year after year 

 without rotation, canker also exhibits its worst form, rendering 

 potatoes worthless and unsightly (see Journal of the Royal Horticultural 

 Societi/, vol. xxxvii, figs. 101, 102). Is Chrysophlyctis, in this country, 

 really more virulent in character than the canker parasite, Spongosjjora 

 solani, or is the supposed greater virulence merely apparent owing to 

 the absence of sufficient information on the canker side ? 



The life-history of Chrysophlyctis is moderately well known, never- 

 theless several important problems remain to be solved, such as (1) 

 the exact nature of the bodies penetrating the tissue and the method of 

 penetration ; (2) the mode of existence for a prolonged period in the soil ; 

 (3) the conditions which favour or inhibit infection. 



It is known that the fungus forms resting bodies (sporangia) in the 

 tubers which when returned to the soil are capable of passing the winter 

 there and may perhaps rest for years in the soil without losing the power 

 to germinate. These sporangia are therefore a prolific source of 

 infection and it is important to realise that infection can be brought 

 about by their means in the following ways : 



1. By planting diseased tubers. 



2. By planting not-diseased tubers removed from infected soil. 

 Ann Biol. i. 13 



