194 
F, T. Brooks. 
were still free from undoubted blight spots on the leaves. Like¬ 
wise all other plants in the plot except those mentioned were still 
unaffected by blight. 
Between July 24th and 28th several small garden plots near 
Plot 1 in Haven Street shewed blight spots on the leaves. 
The weather conditions between June 24th and Aug. 2nd 
were as follows ;—Rain fell on July 10, 11, 12, 14, 15, 17, 22, 23, 
24, 26, 27, and Aug. 2, the other days being dry and warm. It will 
he noted that no rain fell between June 24th and July 10th and 
this dry spell probably delayed the appearance of the disease in 
epidemic form. 
There are several possible explanations of the way in which 
plant A became infected :— 
1. The seed tuber may have thrown up a diseased shoot 
which escaped observation, from which spores were (a) splashed 
upwards by rain to infect the base of the stem and lower leaves, 
and ( b) washed down into the soil to infect the tubers. As stated, 
however, there was no trace of such a diseased shoot. 
2. A diseased shoot which escaped observation may have 
grown up from some other tuber near by, but it is more difficult in 
this case to understand why other plants did not shew 
discoloration at the same time as plant A and why the tubers of the 
latter should be infected. 
3. The plant may have become infected by spores existing in 
situ. It might be supposed, for example, that resting spores in the 
soil at this spot germinated, giving rise to conidia or zoospores 
which may have been splashed upwards to the lower parts of the 
plant and also washed down to the tubers. If so, it is uncertain 
how such spores got into the soil as the previous crop was onions, 
although in view of the widespread opinion amongst practical men 
that potato disease is often propagated by way of the manure, it is 
perhaps of some significance that two years previously the site was 
a fowl run. 
4. A blighted tuber or portion of such near the surface of the 
soil may have given rise directly to conidia, but in view of the 
previous crop, this is unlikely. 
Prom July 22nd onwards, certain other plants in this plot 
already under suspicion of being affected by Phytophthora, became 
attacked by typical blight spots, chiefly, but not exclusively, on the 
laminae of the lower leaves and it appears likely that these were 
derived from spores which arose on certain of the discoloured areas 
noted before this date, but which escaped observation. It is of 
interest that, in this plot, of the plants which did not shew 
