USTILAGINALES 597 



into multinucleate appressoria, as in the Erysiphaceae, before 

 the penetration of the host cell (Lutman, 1910). In many other 

 forms, e.g., in most of the cereal smuts, the hyphae are only intercellular 

 parasites, form no haustoria and take their food directly by osmosis. 

 Even in these, however, the decomposition products of the hyphae seem 

 to cause injury to the host, e.g., in Tilletia Tritici a retardation of growth 

 and increased susceptibility toward Puccinia glumarum (Lang, 1917). 

 In still others, e.g., U. Zeae, the hyphae grow intracellularly, penetrate 

 the individual host cells and cause death. 



Conidia are formed on the host in some genera, as Entyloma and 

 in Tuburcinia Trientahs (Woronin, 1881) and Ustilago Vuijckii (Seyfert, 

 1927). The hyphae form thick, white mats of simple unbranched coni- 

 diophores on the lower sides of the leaves between the epidermal cells 

 or on the filaments which creep around on the epidermis. The conidio- 

 phore repeatedly cut off hyaline pyriform conidia which germinate with 

 germ tubes or, under unfavorable conditions, with secondary conidia. 



In most other genera only the smut spore is known. It develops in 

 certain organs of the host and only on its appearance may the infected 

 plants be recognized as such. In many species, the host is not further 

 deformed by the formation of a sorus. The tissue in which spore 

 formation proceeds is resorbed; thus wheat kernels infected by Tilletia 

 Tritici are recognizable by a slight swelling, a darker color, and a greater 

 spreading of the glumes. Because of the presence of trimethylamine in 

 the smut spores, their intense odor is like that of herring brine. Other 

 species cause characteristic hypertrophies; thus the ovule of Polygonum 

 Hydropiper attacked by Sphacelotheca Hydropiperis is turned into a spore 

 "capsule" which often extends far above the unaltered perianth and, at 

 maturity of the spore, bursts open in valves. In Melandryum the 

 female flowers are induced to form staminate filaments by Ustilago 

 violacea which, as U. Scabiosae, forms its sorus only in the anthers. These 

 filaments are colonized by the fungus and destroyed. In U. Zeae, the 

 parenchyma of the host is stimulated to form gelatinous growths up to 

 the size of a child's head (smut tumors), which are again dissolved by the 

 fungus. In eastern Asia the natives eat as vegetables beet-like stems of 

 Zizania latifolia deformed by Ustilago esculenta (Hori, 1907); and in 

 Polygonum chinense of Java the stem is stimulated by Ustilago Treubii 

 to growths which occasionally appear like Cantharellus and form in their 

 interior a peculiar capillitium which apparently participates in the dis- 

 semination of spores. The number of the spores formed in such a sorus 

 is very large ; in Tilletia Tritici, it averages four million spores per smutted 

 kernel; according to Buller (1909) even twelve million. 



The smut spores, as the teliospores of the Uredinales, arise exclusively 

 on binucleate mycelia. Before their formation the hyphae branch very 

 much and form thick tissues of extremely slender, small cells which, as a 



