110 N. H. AGR. EXPERIMENT STATION [Bulletin 144 



The vegetative portion of a fungus consists of minute threads 

 known as hyphce. A mass of these hyphae is spoken of collect- 

 ively as the mycelium. The white thread-like growth in mush- 

 room spawn is the mycelium. It is this same mycelium w^hich 

 later spreads thru the mushroom bed to obtain the food with 

 which to form the mushroom. With parasitic fungi the myce- 

 lium spreads between or into the cells of the host and absorbs its 

 food material from them. With few, if any, exceptions the para- 

 site obtains its own food, to the great detriment of the host. 



Fungi form no seeds but are reproduced by means of spores. 

 These serve the same purpose as seeds but are produced in much 

 greater numbers and are much more simple in structure. They 

 are too small to be seen with the eye and so light that they are 

 readily scattered by the wind. 



Spores may be divided into two classes, the summer spores and 

 the winter spores. The former are produced in enormous num- 

 bers and serve for the spread of the disease in the summer. 

 They are usually cut off from the ends of special hyphae known 

 as spore stalks or sporophores. The winter spores can endure 

 more unfavorable conditions and serve to carry the disease over 

 the winter and thru dry seasons. They are usually produced 

 in a special protective body known as a pycnidium or perithe- 

 cium. The spores that are produced in perithecia are inclosed 

 in sacs called asci. 



Spores germinate by sending out a germ tube. This tube or 

 hypha may enter the host tissue and develop a new mycelium 

 there. The breathing pores of the leaves and fruit and wounds 

 on the limbs and the trunk of the tree furnish opportunities to 

 gain entrance to the host plant. The fact that the spore can 

 germinate only in the presence of moisture and that the germ 

 tube is thin-walled and delicate gives an opportunity to destroy 

 it before it gains entrance to the host by spraying the host plant 

 with some substance which will be poisonous to the germinating 

 spore and which will slowly dissolve in the dew or other moisture 

 that may be on the plant. The secret of successful spraying 

 is in applying poisons of such a strength and in such a manner 

 that the spores will be killed without injury to the host. When 

 a fungus once gains entrance to the host there is little opportu- 



