32 MICROSCOPIC OBJECTS. 



which have not been near any place in which diseased 

 potatoes have been kept. 



That the above view is correct, microscopic observa- 

 tions on the tuber, and the following statement and 

 remarks, will show. 



Some years ago a Mend of the writer went to reside 

 in a new house in the suburbs of London. The house 

 was remarkably dry, and he observed that remains of the 

 paste he occasionally used for mounting drawings, and 

 which was kept in a small jar in a cupboard, did not 

 become mouldy. This surprised him very much ; for at 

 a former residence the paste would mildew on its surface 

 if kept only a few days. On one occasion it so happened 

 that a little paste was left in a cupboard for a great 

 length of time ; and on examination it appeared covered 

 with mildew, — a circumstance which might naturally be 

 expected.* The curious fact which now presented itself 

 was, that afterwards no paste could be kept in that house 

 for any length of time without mildew being formed on 

 its surface ; thus proving that these minute spores were 

 present in every part of the house, and, being wafted 

 about by the slightest currents of air, were self-sown on 

 the surface of fresh paste. 



The case of the potato, there is httle doubt, will be 

 found to be a parallel one to that of the paste ; and it 



* It may be remarked, that the mildew which forms upon the 

 surface of paste consists of numerous plants, belonging to the 

 family ol Acrogens, called Fungi, and which are highly interesting 

 microscopic objects. 



