180 Plant Biology 



fungi produce heavy-walledj dark-colored, smut spores known as chlamy- 

 dospores (klam' i do spor) (Gr. chlamys, cloak; sporos, spore or seed). 

 The latter are especially prevalent in the ovary tissues of the host plant 

 but may appear in other tissues. The resistant smut spores may be dor- 

 mant until the next spring when each germinates to form a cylindric 

 tube of one to four cells known as a basidium. The latter produces 

 hasidios pores (sporidia). The basidiospores attack host plants, produc- 

 ing hyphae which eventually form smut spores. 



Fig. 66. — Corn smut (Ustilago zeae) showing unbroken tumors at the right but 

 broken and disseminating spores at the left; insert shows chlamydospores of corn 

 smut. (By permission from Botany by Hill, Ov^erholts, and Popp. Copyright, 

 1950, McGraw-Hill Book Company, Inc.) 



In some species of smuts, conidia are also found on the parasitized 

 plant. Thus as many as three types of spores may be formed in certain 

 life cycles. In certain species the basidiospores conjugate in pairs before 

 germination. 



Smuts constitute a common group of about 400 species and are pri- 

 marily parasitic on members of the grass family such as corn (Fig. 66), 

 oats, wheat, rice, rye, barley, etc., where they are responsible for tre- 



