THE FUNGI 



175 



B 



Reproduction. As a rule the formation of spores is confined to the flowers 

 of the host, but almost any part of the plant may show the galls containing 

 spores. In the Corn-smut (Fig. 141) the 

 spores may be formed either in the male 

 flowers of the tassel, or in the female 

 flowers forming the younger ear. The 

 infected tissue becomes enormously en- 

 larged, so that a single kernel may 

 become as large as a walnut. A section 

 of such infected tissue shows the exten- 

 sively branched irregular mycelium of the 

 Smut packed in the intercellular spaces 

 between the enlarged host-cells, and at 

 the ends of the short branches myriads 

 of small black spores are seen, which 

 arise singly or in groups within the ends 

 of these branches. These black masses of 

 spores shimmering through the overlying 

 white tissue give the peculiar livid color 

 to the hypertrophied kernels, which are 

 finally burst open, exposing the dense 

 sooty mass of spores mixed with the disor- 

 ganized fragments of the mycelium and FIG. 141. Ustilago maydis. ^4,stami- 

 the dead tissue of the host. 



nate flowers of Indian-corn, attacked 

 by "Smut." B, mycelium, showing 

 the beginning of spore-formation. 

 C, ripe spores (X600). D, germi- 

 nating spore, developing a promyce- 

 lium, with sporidia, sp. (D, after 

 BREFELD.) 



The spores do not germinate at 

 once, but remain until the next 

 season, when they germinate by 

 sending out a short, thick hypha 

 which becomes divided into a row of short cells, each giving rise 

 to a single conidium. The conidia may multiply by budding, very 

 much like the Yeast-fungi, if grown in a fluid medium. Ordinarily 

 the conidium grows by sending out a germ-tube which penetrates 

 the delicate tissues of the seedling as it appears above ground, and 

 insures its infection by the parasite. 



Tilletiineae. A second order of Smuts, the Tilletiinese, contains also 

 a number of destructive parasites. Tilletia tritici causes a serious 

 disease of Wheat, and Urocystis cepulce is very destructive to Onions. 

 The genus Doassansia attacks various aquatic and marsh plants, espe- 

 cially species of Arrow-head (Sagittaria). 



SUBCLASS II. PROTOBASIDIOMYCETES 



These resemble in some respects the Hemibasidii, and differ from 

 the Autobasidiomycet.es, or higher forms, in having the basidia 

 divided. There are two orders, Auricularinese and Tremellineae. 

 The most important members of the first order are the Busts (Ure- 

 dinales, JEcidiomycetes), resembling in some respects the Ustila- 

 ginese, and like them among the most destructive of plant-parasites. 



