Leaves are the parts of the plant which build up the organic plant 

 food, and so when these are destroyed, the supply of this food is cut 

 off. The cotton leaf rust may be taken as an example of this group 

 of parasites. 



Other fungi inhabit the water-carrying tubes, the wood vessels, of 

 the plant. Their hyphae fill up the cavities of these vessels and so 

 the current of water containing food --alts in solution, which is passing 

 up from the roots to the leaves, is interrupted. These hyphae, of 

 course, absorb part of the food supply which is passing up the vessels, 

 but the damage is comparatively small, compared with that done by 

 the stoppage of the current of water. The dangerous disease of 

 cotton, known as 'wilt,' causes damage in this way. filling up the 

 vessels of both root, and stem with its hyphae and causing the leaves 

 to wilt. The fungus of the rind disease of the sugar-cane is another 

 that inhabits the vessels of the stem. Other fungi similarly attack 

 the walls of the wood vessels and destroy them, and in this way 

 render the vessels incapable of conducting the water current. 



Another group of fungi attack the actively growing regions of 

 the different plant organs, and so stop tin' growth of the organs. The 

 fungus causing the root disease of the sugar-cane may be classed here. 

 The fungus mycelium attacks the growing points of the young roots 

 as they emerge, thereby rendering their further development impos- 

 sible. In this way the plant is unable to absorb the necessary water 

 and food salts from the soil, and so gradually dies of starvation, 

 although the amount of food actually taken by the fungus from it- 

 host is small. 



Canker diseases are caused by fungi that attack the cambium, 

 the tissue that forms new wood. &c, of the stem. At the point 

 attacked the plant is unable to form new wood or new bark, and as 

 this formation goes on elsewhere, a canker is formed. As the fungus 

 grows it gradually spreads, killing the cambium all round the stem. 

 and the death of the plant follows. 



Again other fungi, the hypha? of which live inside the host, 

 kill the plant tissues by the secretion of poisons into the cells The 

 fungi that cause the ■"damping off" diseases may be mentioned as 

 examples of this class. 



Other fungi simply attack the fruits or parts for which the host 

 plant is cultivated. In this way. although the damage done to the 

 plant itself may be slight, the crop, so far as the cultivator is con- 

 cerned, is spoiled. Fungi that cause leaf-spot diseases of tobacco, 

 others that cause malformed fruits, and others that attack the bolls of 

 cot ion and damage the quality of the lint may all he considered under 

 this head. 



There are many other ways in which fungi may cause damage. 

 but from what has already been said, it will easily be seen that a 

 plant has many vulnerable points, and that a fungus which makes a 

 successful attack on any one of these may be as dangerous to the plant 

 as. say. a grazing animal which comes along and eats up the whole. — 

 Tie. in Agricultural News, Barbados, November 7. 



