FARMERS' INSTITUTES. 55 



SOME FUNGOUS DISEASES OF PLANTS. 



BY B. 0. LONGYEAR, BOTANIST, EXPERIMENT STATION, AGRICULTURAL COLLEGE, 



MICHIGAN. 



I would like to take the audience into the garden, through the or- 

 chard and fields, and into the woods, and while on this little journey 

 we might admire the beaut}" of leaf, flower and fruit there seen. We 

 would also meet with some unpleasing things. One of the unpleasant 

 features of travel through oriental countries, especially to an Amer- 

 ican, is said to be the great number of beggars which swarm about the 

 traveler in the cities. They frequent the most noted streets, lie at the 

 doors of beautiful temples and palaces, and display their deformed 

 limbs, or uncover their loathsome sores to the gaze of the traveler, in an 

 attempt to excite his compassion. 



In like manner, while we are gazing in ecstacy at the lovely and deli- 

 cate tints of flowers and inhaling their fragrance, while delighting in 

 the anticipations of fruit to follow, we are quite sure to find some of 

 our plants holding out their deformed and cankered limbs or their 

 scorched and withering leaves in mute appeal, while the scarred fruits 

 later in the season will touch our sympathies as deeply, perhaps, as the 

 afflictions of the beggars. 



Most of the diseases to which plants are subject are due to the 

 attacks of parasitic fungi and it is to such diseases that I shall confine 

 myself. Probably the term fungus does not convey to most persons a 

 very definite idea of these organisms, consequently it seems desirable 

 to briefly discuss their nature in this connection. 



Fungi are plants of a low order. Familiar examples may be found 

 among the mushrooms, moulds, mildews, rusts, smuts and a large num- 

 ber of others which cause the decay of fruit, leaves and timber. The 

 true parasitic fungi are those which exist and grow upon, or within, 

 the tissues of living plants, and which cause so much destruction and 

 disfiguring of our cultivated plants. Most of these fungi are very 

 simple in structure. They consist of a vegetative part, usually com- 

 posed of delicate, branching, tubular threads known as mycelium. This 

 is the part of the fungus which does the harm to the plants on which it 

 feeds, as it has the power not only of absorbing the nutriment from the 

 cells of its host, but also of killing the living part of the host plant. 

 However, in some cases the mycelium produces at first a stimulating 

 effect on a small part of the plant attacked, so that the cells become mul- 

 tiplied or enlarged, thus producing various swellings or distortions of 

 the affected portion. At the same time, the cells of the host plant at 

 this point may become gorged with starch or other food material, which 

 is finally appropriated by the mycelium of the parasite, thus robbing 

 the host throughout a considerable portion. 



In some cases, the mycelium does not extend far, but is localized, 

 thus producing spots of swollen or dead tissue, whichi may eventually 

 drop out thus causing perforations or deep pits. In others, the mycel- 



