120 THE AMERICAN MONTHLY [July, 



yet reached the top of the plant ; one never sees the top of an ear diseased 

 and the base sound. It is an undisputed fact that in smut the disease grows 

 inside the stem from the bottom upwards.* 



Now take a dwarfed and diseased cluster of grains and chafty scales from 

 a wheat-spike and magnify with a lens five diameters. The chafty scales are 

 rent and torn, and from every fissure the fine sooty powder is bursting out. 

 If the cluster or spikelet is cut across it will be noticed that the whole fari- 

 naceous material of the interior has been replaced by one compact mass of 

 fine black dust. The upper part of the stem of the corn, and the scales and 

 grains alike, are infested and choked by the sooty powder. Take a fragment 

 of one of the chaft' scales and magnify it with a mici'oscope 25 diameters, 

 numerous cracks, some large, others small, vv^ill appear, and from every crack 

 the fine jet black powder will be seen bursting out from the inside. 



Every grain of this black powder is a minute spore or seed of the smut 

 fungus. In an earlv stage of the disease, a state seldom noticed by farmers, 

 the fungvis is colorless ; it grows within the stems of corn as fine transparent 

 threads, immeasurably finer than any spider's thread. These threads at 

 length reach the ears, the scales, and the infant grains. Here they form 

 within the substance of the plant a whitish viscous mass of threads and cells, 

 and this mass gives rise to an immensely large number of spores which 

 quickly become black in color, burst through the tissues, and so reach the 

 outside air. The fungus always grows so luxuriantly in the ears that nothing 

 is ultimately left of the part which should bear the grain but a few dry vege- 

 table threads, which are speedily torn apart, and this wreck of what should 

 be the ear is soon carried away by the wind. As a rule, the ears, whether 

 of wheat, oats, or barley, are totally destroyed by the fungus. 



The particles of black powder are excessively minute in size. If they are 

 magnified 400 diameters, they are seen as at c. An idea of their extreme 

 smallness may be gained by comparing them with a seed or spore of the po- 

 tato fungus, illustrated on the same scale at </, or with a seed or spore of the 

 putrefactive mildew of onions, shown on the same scale at e. Two hundred 

 spores of smut fungus could find ample room inside a single spore of the 

 onion fungus (e), Pero?iospora Schleideniana. Owing to their extraor- 

 dinary smallness, the spores of the smut fungus find their way everywhere ; 

 they are also produced in such profusion that in a smutted district there is 

 not an inch of ground free from them. 



The spores of the smut fungus, on germination, of course reproduce the 

 disease in cereals. They do not germinate on dry ground, nor in dry air, but 

 retain their vitality, if kept dry, for at least a year. Smutted ears have been 

 kept in papers for a year in a dry room, and at the end of this time the spores 

 of the fungus had suffered no injury. The spores, like ordinary seeds, re- 

 quire moisture for germination, and if they are put in a film of water 

 they will germinate in from six to twelve hours. The very highest powers 

 of the microscope are required to see this germination, and if objectives are 

 used which magnify one thousand diametei's, germinating smut-spores will 

 be seen as aty, g^ h. On germination, the outer coat of the spore bursts or 

 cracks, and out of the fissure a minute transparent bladder emerges, which 

 by budding soon gives rise to a second cell or bladder, as aty. As growth 

 is continued, further budding takes place, at right and left, as well as at the 

 top of the buds, as shown ■a'i g and h. If the spores are grown in the juices 

 from farmyard manure diluted with water, the budding becomes much more 

 profuse, as at /. This bursting and budding of the minute spores, which can 

 be observed under the microscope, takes place naturally in the ground in 



*Also easily proven by study of the hypha? in the stem ; the youngest ones being found in the youngest tissues. 



