196 BOTANY. 



sues of flowering plants. Like the Eusts, they send their 

 parasitic threads through the tissues of their hosts, and 

 afterwards produce spores in great abundance, which burst 

 through the epidermis. There is a still greater simplicity 

 of structure in the plants of the present order than in the 

 Eusts, probably due to a greater degradation through ex- 

 cessive parasitism. 



357. The parasitic threads of the Smuts are well defined, 

 and consist of thick-walled, jointed, and branching fila- 

 ments, which are generally of very irregular shape. They 

 grow in the intercellular spaces and cell-cavities of their 

 hosts, and send out suckers (hausioria), which penetrate 

 the adjacent cells much as in the Mildews. The parasite 

 generally begins its growth when the host-plant is quite 

 young, and grows with it, spreading into its branches as 

 they form, until it reaches the place of spore-formation. 

 In perennial plants the parasite is perennial, reappearing 

 year after year upon the same stems, or upon the new 

 stems grown from the same roots ; in annuals it must ob- 

 tain a foothold in the young plants as they grow in the 

 spring. 



358. The life-history of the Smuts has not yet been com- 

 pletely made out. Two kinds of spores have been ob- 

 served in many species, and the germination of the spores 

 has been carefully studied, but the sezual organs (if any 

 exist) have not yet been discovered. 



359. 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 become semi-gelatinous and form spores in- 

 ternally. There is much crowding and distortion of these 



