1922.] Anthbacnose of the Cucumber Under Glass. 471 



Material was collected with instruments sterilised by dipping 

 in spirit and flaming with a pocket petrol lighter, and was con- 

 veyed to the laboratory in sterilised plugged specimen tubes. 

 The investigations were carried out in nurseries where the 

 disease had never appeared, as well as those badly attacked in 

 the previous year, and examinations were made immediately the 

 crop was removed and also after the houses had received the usual 

 winter treatment prior to the planting of the next month's crop.. 



The following materials were examined : — 



(1 ) General debris found between the " overlaps " in tbe glass structure 



(2) Samples of decayed wood from holes in "plates,'-* " bars " etc. 



(3) Samples of old decayed posts. 



(4) Samples of decayed wood from tanks in the houses. 



(5) Samples of paper used for filling cavities and packing warped 

 ventilators. 



(6) Samples of straw manure from the beds. 



(7) Samples of straw manure from the original heap. 



(8) Market boxes or " flats." 



Part of each sample was examined in the laboratory, while 

 another part w r as placed in a flask, kept moist for 14 days and 

 shaken up with water w T hich was afterwards sprayed over 

 young cucumber seedlings. 



Material from glasshouses where the disease had not occurred 

 previously did not yield the fungus. Materials obtained from 

 diseased houses showed the fungus to be present and young 

 plants were infected by many of the water suspensions tested. 

 The main conclusions may be stated briefly as follows : — 



(1) The present methods of cleansing glasshouses during 

 the winter months are not sufficient to exterminate centres of 

 infection of Colletotrichum olitjochaetum which may exist from 

 a previous diseased crop. 



(2) Infection is more abundant immediately after the dis- 

 eased crop has been removed than after the period of winter 

 rest, but sufficient survives to carry the disease over from one 

 season to another. 



(8) The fungus may live occasionally in the debris which 

 collects in the overlap between two panes of glass, but except 

 in old houses this does not form an important source of 

 infection. 



(4) The fungus may carry on a saprophytic existence in 

 rotten wood in the house and paper used for blocking holes, 

 and these constitute important sources of infection. 



(5) Straw manure removed from beds in infected houses 

 was found invariably to harbour the parasite and when allowed 

 to remain unburnt in a heap outside the houses — a common 

 practice — must be a centre for the spread of the fungus. 



