466 Agricultural Journal of Victoria. 



were met with. In such cases, however, it was readily seen that the 

 normal conidium, with its tapering beak, became modified in such a 

 way that the ultimate segment of the beak became cup-shaped and 

 bore a secondary conidium at the apex. Jones and Grout in America 

 were the first to note these chains of conidia, but they failed to draw 

 attention to the modification in the form of the beak of the conidium, 

 necessary before the chains could be formed. It is a nice point to 

 settle whether the fungus concerned should not be more properly 

 termed a Macrosporium, as named by the original describers, or an 

 Alternaria, as suggested by Jones and Grout. The matter is mainly 

 one of scientific interest, but since the normal habit of the fungus 

 growing under natural conditions as a parasite is to produce its 

 conidia singly and not in chains, it seems tha,t the balance of evidence 

 is in favour of the former name. No record has, so far as I am 

 aware, been made of the occurrence of chains of conidia growing 

 naturally upon potato leaves. 



The difference is very striking between the normal tapering beak 

 of the naturally formed conidia in Figs. 3, 5, and t) and the conidia 

 with cup-sha])ed extremities produced under artificial conditions, as 

 in Figs. 8 and 9. 



Treatment- 



In certain parts of Gippsland this disease has been a standing 

 grievance with potato-growers for a number of years, and the only 

 explanation they can offer as to its occurrence is that the seed has 

 run out, and the evident remedy is to get new seed from another 

 district. It is not considered safe to plant the same potato seed for 

 more than two seasons, and even in the second season there may be a 

 considerable loss, even as much as 20 per cent. I examined a number 

 of fields under similar conditions and found considerable variation. 

 In one field which produced six tons of good, sound tubers the 

 previous year, in the following year the growth was very unsatis- 

 factory, as from their first appearance above ground the stalks were 

 weak and sickly, and a number never came up at all. In an adjoining 

 paddock, where the soil was similar and the new seed potatoes planted 

 the same week, and for the first time, the produce was at the rate of 

 11 tons per acre, without misses, and the plants all strong and 

 healthy. 



The growers in this district have found out by dear-bought 

 experience, that it is necessary to have fresh seed every season at 

 least, but tkey have no idea as to why this is useful in checking the 

 disease. I take it that since this particular fungus is what is known as a 

 weak parasite, it can only do serious damage when the vitality of 

 the plant is lowered from some other cause. The plant from fresh 

 seed resists the disease, because it is more vigorous in its growth, and 

 less likely to let the fungus gain a footing in its tissues. Therefore, 

 the first recommendation is to adopt all those measures which tend to 

 produce a healthy and vigorous plant, such as thoroughly-matured 

 seed from a clean district, deep ploughing, manure where necessary. 



