222 



BOARD OF AGRICULTURE. 



In the case of the moulds which do not grow upon living 

 plants, the mycelium forms usually a mass looking more or 

 less like cotton-wool. In those which inhabit living plants, 

 the threads wind about amongst the cells of the plant on 

 which they are growing, and, when seen on the surface, 

 appear like a fine web or frost-work. 



As has just been remarked, for a great part of their exist- 

 ence fungi consist of a mass of threads : but, under favorable 

 circumstances, reproductive bodies known as " spores " are pro- 

 duced ; and, in producing them, the threads undergo a variety 

 of changes, some of which are very complicated. There are 

 no true seeds or flowers in fungi ; but in their power of ger- 

 minating, and reproducing the 

 species from which they were 

 derived, the spores of fungi cor- 

 respond to the seed of higher 

 plants. Unfortunately for the 

 easy understanding of the sub- 

 ject, the mode of production of 



Fig. 1. 



the spores is a difficult subject to follow ; and it is made more 

 difficult by the fact that many, perhaps most, fungi produce 

 more than one kind of spore, a state of things to which we 

 have nothing directly corresponding in the higher plants with 

 which we are familiar. 



After this preliminary description of what is known as a 

 " fungus," let us examine in detail the disease known as the 

 " black knot." The knots are most striking in the autumn 

 and winter. If we make a microscopic examination of a knot 

 gathered in mid-winter, we shall find that it is composed 

 partly of a fungus, and partly of the diseased and distorted 

 cells of the plum-stem. The white threads of the fungus are 



