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 
Jd G excessive parasitism. 
haters gat 405. The parasitic threads of the 
Smuts are well defined, 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 
