374 
Annual Report for 1913 of the Botanist. 
permanent pastures. One appeared to be the “blowings” 
of a wheat crop grown on land infested with black-grass 
( Alopecurus agrestis) and couch grass since these were the 
only grass seeds it contained. The other consisted of the 
screenings of various crops. It contained about 5 per cent, 
of the seeds of various weed plants occurring in pastures, 
whilst the useful seeds amounted to about 1 per cent. The 
remainder was a mixture of wheat, barley, charlock, corn 
buttercup, goosegrass and wild onion. 
Plant Diseases. 
Enquiries with regard to fungoid diseases of plants were 
less numerous than in the preceding year — their total aggregat- 
ing 47. They would have been still less had it not been for a 
number of outbreaks of wet rot in potatoes during November. 
Foi the sake of convenience the more important enquiries are 
described in short sections devoted to each crop. 
Potatoes .— Towards the end of July several members 
sent specimens of potato foliage in order to ascertain whether 
the discolouration of the leaflets was due to the attacks of 
Rhytophthora infestans. A microscopic examination showed 
this to be the case and the application of the usual preventive 
measure, namely spraying with Bordeaux mixture, was 
recommended. Later reports showed that this effectively 
checked the further spread of the disease. After the crop had 
been lifted tubers showing advanced stages of decay were sent 
in from various parts of the country. In two cases the tubers 
were from fields which had been sprayed on which it was 
definitely stated that no disease had appeared. In other cases 
a late attack had been experienced but as the haulm was dying 
off, no ill consequences were anticipated. Nevertheless the 
potatoes began to rot rapidly in the clamps. The disease was 
apparently the well-known, but little investigated “ wet-rot.” 
Cultures were made from the tubers and amongst others a 
bacterium was isolated having the general characteristics of 
Bacillus amylohacter which is generally considered to be 
the cause of the decay. In all probability this had attacked 
tubers already infected by PhytojAithora. 
One undoubted case of the Black Stalk-rot due to Bacillus 
melanogenes was sent from the Lincoln Fens. When plants 
are attacked the leaves become first a paler green, then yellow, 
and curl over so as to expose the lower surface. At the same 
time the base of the stem turns black and watery. An early 
attack results in the death of the plant. No curative measures 
are known at present but in view of the fact that the bacterium 
may find its own way to the tubers and consequently be planted 
