46 DISEASES OF TROPICAL PLANTS 



CH. 



attack the young grains which they destroy and convert 

 into a rather hard spherical or elongated body composed 

 of a compact mass of mycelium. On its surface are 

 produced thousands of condiophores. At the same 

 time a sweet fluid is produced which attracts insects, 

 and ensures a distribution of the spores. In due time 

 this fungus body turns black, and becomes the ergot of 

 commerce. After a resting period small cylindrical 

 stalks grow out, and on the end of each is a spherical 

 body which is pitted by very small pear-shaped cavities. 

 Within these cavities are the sacs or asci containing the 



O 



spores. The ergots are poisonous, frequently causing 

 sickness, 'and often causing death of animals which feed 

 upon the diseased grain. They also cause sickness, and 

 occasionally death, of people who unsuspectingly eat 

 bread made from the diseased grain. They possess 

 properties which make them valuable in medicines. 



Another genus of this order is Cordyceps (Fig. 4 29), 

 the species of which attack insects and their larvae, and 

 eventually cause their death. The body of the insect or 

 larva .becomes thoroughly infested with the mycelium, 

 which eventually assumes the character of a sclerotium 

 and in due time sends up club-shaped, frequently bright- 

 coloured bodies. These bodies contain numerous small 

 cavities, within which are the asci or sacs containing 

 the spores. These fungi are very common in the 

 tropics, and no doubt are very beneficial in the de- 

 struction of insect pests (see page 260). 



The genus Nectria includes a number of species, all 

 of which have either yellow or red fruiting bodies. They 

 are the cause of a number of diseases of tropical plants 

 occurring on the cacao, tea, rubber, and many forest trees 

 (pp. 175, 183, 191, 253). The fungus enters the host 

 through a wound and makes its growth in the water- 

 conducting tissues of the wood. It attacks the cambium, 

 and gradually girdles the tree or branch, causing death. 

 It continues to live in this dead wood as a saprophyte, 

 and finally comes to the surface, forming clusters of 

 soft, bright red or yellow bodies. Upon these bodies are 



