236 PHYLUM VII. CARPOMYCETEAE 



tissues of Flowering Plants. Like the Rusts, they send 

 their parasitic threads through the tissues of their hosts, 

 and afterward produce spores in great abundance which 

 usually burst through the epidermis. 

 There is a still greater structural degra- 

 dation in the plants of the present order 

 than in the Rusts, probably due to their 

 excessive parasitism. 



406 * Tne P arasitic threads of the 

 Smuts are well denned, and consist of 

 thick-walled, cellular, branching filaments, which are 

 generally of very irregular shape. They grow in the 

 intercellular spaces and cell cavities of their hosts, and 

 some send out suckers (haustoria) , which penetrate the 

 adjacent cells much as in the Mildews. The parasite 

 generally begins its growth when the host plant is 

 quite young (meristematic) and grows with it, spreading 

 into its branches as they form, until it reaches the place 

 of spore-formation. In perennial plants the parasite 

 may be perennial, reappearing year after year upon the 

 same stems, or upon the new stems grown from the same 

 roots; in annuals it must obtain a foot-hold in the young 

 plants as they grow in the spring. 



406. The life history of the Smuts has been made out 

 for but few species. Three kinds of spores (conidia, 

 teliospores and sporids) have been observed in many 

 species, and their germination has been carefully studied, 

 but the sexual organs (if any exist) have not yet been 

 discovered. 



407. The Smut of Indian corn (Ustilago maydis) is 

 very common in autumn. The parasitic filaments are 

 found in various parts of the host, and at last those which 

 reach the young kernels or other succulent parts become 

 semi-gelatinous and form spores internally. There is 



