58 



plant diseases comprises those which attack fruits. In 

 this lecture we shall consider the most common disease of 

 seedlings which is known as the "Damping off" disease. 



Before dealing in detail with this, however, let me 

 recall some of the more essential features in the structure, 

 nutrition and life history of the more common fungi, facts 

 with which you are no doubt, to some extent, already 

 familiar. In any of the fields and lanes around our large 

 towns, especially in autumn, it is possible to find examples 

 of the larger fungi such as mushrooms and toadstools. 

 Whilst the colour and form of the part which we see above 

 ground are often striking, in reality this is only the repro- 

 ductive part of the toadstool or mushroom plant, just as 

 much as the flower and fruit are the reproductive parts of 

 the higher plant. It is true that the mushroom as we 

 generally see it, appears above ground, sheds its spores 

 and decays all within a few weeks; but the vegetative part 

 of the plant lives in the ground for a very considerable 

 time before it enters on the reproductive phase. 



The bricks of so-called mushroom spawn contain 

 quantities of fine interlacing threads of fungus in manure 

 which are really the vegetative part of the mushroom. 

 Under the microscope these filaments are seen to consist 

 of long branched tubes. These tubes are divided up into 

 chambers or cells by cross partitions, and each cell is 

 lined with the jelly-like semi-transparent living substance, 

 protoplasm. Within this are drops of water and oil as 

 well as certain denser granules, but filaments of fungi 

 never contain the green colouring matter found in higher 

 plants. The protoplasm is the living part of the cell, 

 and food material is taken in from the soil, or manure 

 through the protecting cell membrane. Such food 

 material often appears stored in the tubes as drops of oil. 



Although the filaments of the vegetating mushroom 

 plant are not bound together into a complex plant body 

 like the cells of flowering plants, yet the loosely inter- 

 woven threads behave as a whole, and after w r eeks or 

 months of vegetative growth give rise to the definite fruit 

 bodies consisting of numberless aggregated filaments. 

 These reproductive bodies usually possess a stalk bearing 

 an expanded cap from the under side of which project the 

 radiating gills. Upon the surface of the gills are borne 

 large numbers of minute round or oval spores. Each 

 spore is really a single tiny cell so small that it can only 



