SUMMER MEETING. 



47 



of an inch long. A cross section of the host plant shows the receptacles, 

 or holes in which the spores are lodged, to be entirely in the bark, bnt the wood 

 is enlarged in the same proportion as the outside. It is very porous, with regu- 

 lar layers much distorted like a knot. When a spore is within the bark it 

 begins to multiply and crowd out the walls of the receptacle which is of the 

 shape of a spheroid, which is about as long as half the thickness of the bark 

 and contains many hundreds of spores. As these increase in size and numbers 

 they burst through the surface of the bark and throw out a cylindrical shaped 

 tube. This, as the spores grow, splits into numerous longitudinal fibers as 

 before mentioned. (See drawing.) 



The cells of the bark are filled with a pulpy, black substance, and the cell walls 

 are thick and irregular. The spores (see drawing) are about one-thirtieth of a 

 millimeter long, one-quarter wide, and one-fiftieth thick, and are about like an 

 ■egg in shape. The central portion is a dark colored mass with oolitic surface 

 and is surrounded by a concentric layer of lighter colored mass. The surface 

 of spore is somewhat irregular. I have not found out how the fungus is 

 fertilized. 



The illustrations are shown in figure 22. 



Dr. Beal : Concerning corn smut, we shall now hear from one who has done 

 some good work. 



H. B. Cannon : I shall speak a few words on the fungus known as corn 

 smut, Ustilago maydis. The appearance of this in the young ears and stalks 

 in mid-summer is familiar to every one, as the affected parts are much 

 swollen and distorted. At the later stage of development it is black in color. 

 Corn smut is a fungus, or one of the low orders of plant life. It starts from a 

 spore (corresponding to the seed of the higher plants) in the spring at or about 

 the same time that the young corn plant begins to raise above ground. During 

 the season this fungus develops within the tissues of the corn plant, deriving its 

 support directly from them. When I he spore starts it sends out the mycelium, 

 which branches again and again as it penetrates the host tissue. As develop- 

 ment proceeds the corn plant is found to have this mycelium in every part. 

 When it comes to be nearly mature, this mycelium in the rich tissues of the 

 corn kernel, begins to fruit, sending out spore-producing hyphm in such num- 

 bers that they anastomose with each other, forming a thick and intricate mass. 

 [Numerous irregular bunches are formed along the hypha?, which, perhaps, aid 

 in drawing nutriment from the host tissue. In the gelatinous mass of hypha 

 the young spores lie embedded in all stages of development. Where a hypha 

 can be separated from its neighbors, the spores within it are seen to be in suc- 

 cessive stages of development; those nearest the point of attachment are the 



youngest ones, mere spots of condensed 

 protoplasm, while the gradation to the 

 other end shows the spores becoming 

 larger, darker in color, until the last 

 one is nearly ready to break away, a 

 black globular spore. At the end of 

 the season the mass of the hypha? be- 

 come absorbed, dry up, the connecting 

 tissues break away, and the spores 

 breaking through the epidermis of the 

 corn, are spread by the wind everywhere. 

 The spores themselves are microscopic 

 oojects, in diameter from .08 to .11 m. 



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Fin. 



