238 NEBRASKA STATE HORTICULTURAL SOCIETY. 



remaining intact. In the last mentioned cases the berry or "seed" 

 may show an increase of size or a modification of form with the com- 

 plete destruction of all its tissues except a surrounding membrane which 

 serves to confine the mass of smut spores. When the membrane is 

 ruptured the interior brown mass crumbles to powder, since it is simply 

 a loose aggregate of spores which has been formed at the expense of 

 embryo and endosperm. Wheat from fields infested with bunt is often 

 dark in color, due to the immense numbers of spores lodged upon the 

 surface of the kernels and especially collected in the "brush" or tuft 

 of hairs at the distal ends of the berries. 



As a result of the stimulating effect of a fungus parasite, parts or 

 organs of the host plant may exhibit variously formed excrescences or 

 malformations. These malformations may be in the form of pustules 

 or small, blister-like elevations upon the surface of the leaf or stem, 

 as in the "white rusts," or the blistered area may be quite extensive 

 and cause more or less deforming and rolling of the leaf, as in peach 

 "leaf-curl." Sometimes the abnormal formation is iti the form of a 

 smut mass or tumor which when mature is filled with a brown or black 

 powder, the spores of the fungus. In the smutted corn plant these 

 tumors may occur on any part of the plant, not a single aerial organ 

 being exempt. The so-called "cedar apple" is a good illustration of a 

 fungus gall. These brown cedar apples may be present on the cedar 

 trees in large numbers in case of trees that stand adjacent to an apple 

 orchard, and they may vary in size from about that of a radish seed 

 to nearly two inches in diameter. In several cases I have known people 

 to admire these "cedar apples" as the true fruit of the cedar, little 

 realizing that this fungus may often seriously affect the life of the cedar 

 and greatly impair the productiveness of adjacent apple orchards. 



Here may also be mentioned the disease of plums and cherries known 

 as "black-knot." This disease is often not noticed until the conspicuous 

 black enlargements become evident later in the season. The enlarge- 

 ments are somewhat irregular, roughened, and generally extend for some 

 distance along the length of the affected twigs. When young or in the 

 early spring the newly-formed knots are olive green in color. In this 

 condition they produce a crop of spores that spreads the disease, while 

 later the older knots produce a second kind of spore. The fungus that 

 causes the black knot lives perennially in the twigs and branches and 

 consequently new growths appear each year unless the affected limbs 

 are pruned off. In several sections of the state plum orchards are 

 seriously affected and it is not uncommon to find wild plums in many 

 of the canyons covered with malformations of the character described. 



In some fungus diseases the malformations do not show as pro- 

 nounced enlargements. This is true in our common potato scab in 

 which irregular roughened areas appear over the surface of the potato. 

 An abnormal development of the corky tissue may result in a slight 



