BASIDIA-BEARING FUNGI (SMUTS) 1 79 



condition and without external manifestation of infection until in its 

 fruiting stage, when it breaks through the tissues of the host, appear- 

 ing at the surface. In perennial plants, the mycelium may live in the 

 perennial parts, each year extending into the new growth. Eventually, 

 the mycelium becomes conspicuous in certain organs of the plant. It 

 may develop abnormal growths, or cause swellings in the stem leaves, 

 flowers (anthers, ovaries), or fruits of the host. Here the hyphae break 

 up into chains of spores, which develop thicker walls than the hyphal 

 cells from which they arose and are known as chlamydospores (xXayuus, 

 xXctfxvdos = a cloak + (rwopa = a seed). The hyphal cells between the 

 spores undergo almost complete gelatinization, which gelatinized cells 

 are used probably to nourish the developing spores, as at maturity the 

 spores lie loosely surrounded in part by the diseased cells of the host 

 ready to be discharged as the adjoining hyphal and host cells dry up 

 and completely disappear. The chlamydospores, which make up the 

 smutty, or sooty masses, are usually thick-walled and, being small, 

 4 to 35^t, they are easily disseminated. They are usually spherical, or 

 spheroidal, but may be ovoid, eUipsoidal or even oblong. They are 

 simple, i.e., consisting of single cells, but they may be united into spore 

 balls, which may have an external coating of sterile cells. The galls 

 of the chlamydospores may be smooth, or echinulate, or reticulate with 

 a network of ridges, or wings. Their color may be yellowish, reddish 

 or olive-brown, violet, or purplish, and the dark-colored spores in mass 

 may appear to be black or dark amber-brown. Sori are masses of the 

 spores that break out singly, or in clusters, on the various organs of 

 the hosts. These clusters are protected by their coverings of the tissue 

 of the host. The sori may be dusty and easily broken up, while in 

 other species, they may be hard and the spore mass is gradually 

 disintegrated. 



The wind is undoubtedly one of the principal agents in the dissemi- 

 nation of the smut spores, but it was found that no smut spores could 

 be demonstrated in spore traps set up at the University of Manitoba 

 by BuUer farther distant from the infected fields than 250 yards. Man 

 distributes the spores through unclean agricultural methods, such as 

 using old grain bags over and over again, and in sowing seed to which 

 the smut spores are attached. The threshing machine is an active 

 agent in the spread of smut spores, and the farmer should see that his 

 machine is carefully cleaned from one operation to another. 



