Simple Plants Without Chlorophyll — Fungi 181 



mendous crop losses. In the smut of corn, Ustilago Zaea (us ti -la' go; 

 ze' a) (L. ustilago, thistlelike plant; zea, kind of grain), the tumorlike 

 masses of smut may appear on any part of the plant (Fig. 66). When 

 these tumors mature in the summer or fall, they are masses of black 

 chlamydospores. The latter usually germinate the next spring or summer 

 to infect new corn plants. The hasidios pores, formed on the hasidia, 

 produce germ tubes capable of infecting any part of the corn plant. The 

 resulting mycelia mass together at definite points and break out as the 

 smut tumors. The latter are white at first but become black as the 

 chlamydospores mature. Annual losses in the United States due to corn 

 smut are estimated at $100,000,000. 



4. Rusts. — Rust fungi are parasitic on various flowering plants and 

 ferns. They are called rusts (A.S. rust, red) because of their reddish- 

 brown spores on the surface of the leaves and stems. Hyphae penetrate 

 the tissues of the host plant. A rust may parasitize two unrelated species 

 of plants, alternating between the two hosts. 



A very destructive rust is the black stem rust of wheat (Fig. 67) known 

 as Puccinia graminis (puk -sin' i a; gram' in is) (Puccini, an Italian 

 anatomist; L. graminis, grass). The life cycle of this wheat rust may 

 be briefly described as follows: 



In the summer the hyphae live in the stems and leaves of wheat where 

 the blisterlike uredosori (uredinia) (u -re' do so ri) (Gr. uredo, blight; 

 soros, heap) contain many unicellular, rough, reddish-orange, wind- 

 disseminated, summer spores called uredospores (Fig. 67). These spores 

 may infect other wheat plants and are known as the "red rust" of wheat. 



In late summer the hyphae form black pustules known as teliosori 

 (telia) which produce thick-walled, resistant, brownish-black, winter 

 spores called teliospores (teleutospores) (te'liospor) (Gr. telios, end; 

 sporos, spore) (Fig. 67). This is the "black rust" stage. The teliospores 

 remain dormant on wheat straw and germinate next April or May. Each 

 germinating teliospore produces a clublike basidium with its four basidio- 

 spores (ba -sid' i o spor) (Gr. basis, base or club; sporos, spore) which 

 are wind borne to the common, wild, European barberry (not the culti- 

 vated Japanese barberry) . 



The basldiospores (Fig. 67) germinate and send hyphae into the bar- 

 berry leaves, while the yellowish-red spots on the upper surface form 

 small, flask-shaped pycnia (spermogonia) (pik'nia) (Gr. pyknos, 

 crowded); (sper mo -go' ni a) (Gr. sperma, "seed"; gonos, offspring). 

 The pycnia produce small, unicellular pycniospores (spermatia) at the 



