210 MANUAL OF POISONOUS PLANTS 



Hemibasidii 



Mycelium, local or wide-spread, hyaline, septate, branched, becoming com- 

 pact and giving rise to endogenous spores; the chlamydospores ; color varies, 

 in germination the spores produce a promycelium of terminal or lateral sporidia. 

 These may propagate by budding like the yeast plant. The families are Ustila- 

 ginaceae and Tilletiaceae. 



HEMIBASIDIALES 



This includes two families mentioned in the Hemibasidii. 



USTILAGINACEAE, SchrOt 



Usually parasitic fungi in the tissues of living plants; sori usually exposed, 

 forming dusty masses ; spores germinate by means of the septate promycelium 

 which gives rise to terminal or lateral sporidia. In some cases, these multiply 

 like the yeast plant, or else produce infection threads. The order contains about 

 300 species, with the following genera in North America : Ustilago, Sphacelotheca, 

 Melanopsichium, Cintractia, Schizonella, Mykosyrinx, Sorosporium, Thecaphora, 

 Tolyposporium, Tolyposporella, Testicularia. Many plants of the order are 

 destructive parasites occurring upon economic plants like millet, timothy, pink, 

 etc., and one species, the Ustilago esculenta on Zizania laiifolia is edible, being 

 used by the Japanese for food. 



Ustilago, Pers. Smuts 



Mycelium septate, branched, gelatinous, sori on various parts of the host, 

 at maturity dusty, usually dark colored; spores single produced in the fertile 

 threads of the mycelium, the latter entirely disappearing at maturity; promycel- 

 ium septate, sporidia terminal or lateral, producing infection threads; secondary 

 spores formed in the manner of yeast in nutrient solutions. The largest genus 

 of smuts. About 250 or 260 species. Many of them are destructive parasites 

 on cultivated and wild plants. 



The Ustilago minima occurs upon the porcupine grass, (Stipa spartea), and 

 the Ustilago bromivora upon the brome grass. 



Ustilago Zeae. (Beck). Ung. Corn Smut 



Sori in the female or staminate inflorescence, leaves and nodes usually 

 forming irregular swellings of variable size; at first covered by a membrane 

 consisting of the gelatinized threads and tissues of the plant; soon rupturing, 

 which exposes the blackish or brownish spores; spores sub-globose or spherical 

 or irregular; echinulate 8-11 A' or sometimes 15 jit long; spores germinate readily 

 under favorable conditions; spore consists of an outer wall, which is spiny, 

 and an inner more delicate, the endospore ; the germ tube or promycelium as it 

 is called, normally bears lateral bodies, the sporidia, but under more favorable 

 conditions of food .these may branch and bear secondary conidia. If the nutrient 

 material is not exhausted this process of budding may be continued for a long 

 time. These spores may propagate in a decoction of manure. It will then be 

 seen that these budding conidia may be a center of infection. 



The conidia as well as the secondary conidia are blown about by the wind 

 and under proper conditions cause the infection of the corn plant. Several 

 years ago Mr. F. C. Stewart made some extended studies of the germination 

 of corn smut in which it was shown that the thermal death point of smut 



