USTILAGO. 293 



Ust. grandis Fries. Eeed-smut. (Britain.) This frequents the 

 haulms of Phragmites communis (also Typha latifolia and T. 

 minor) ; the internodes of the host in consequence swell out 

 and appear as if the stem carried one or more bulrush-heads. 

 The mycelium permeates the whole host-tissue and produces 

 spores, which escape as a black dust on rupture of the epidermis. 

 According to Kiihn, the spores are capable of immediate ger- 

 mination and retain their vitality for a whole year. A 

 four-celled promycelium is produced and becomes detached from 

 the spore ; then follows an abjunction of oblong conidia from 

 the septa of the promycelium. In nutritive solutions, Brefeld 

 found that germination took place in the same way, but more 

 rapidly and vigorously. Numerous conidia are produced, but 

 these only rarely give off secondary conidia, and then only a 

 single one ; more commonly they produce promycelia, as the 

 spores did, and conidia again arise from these ; yeast-like 

 sprouting does not occur. The resting-spores may continue 

 to give off promycelia in succession for some time. On ex- 

 haustion of nutrition the cells of the promycelium, as well 

 as the conidia, develop into mycelial threads, to which alone 

 Brefeld ascribes the capacity for infection. 



Ust. longissima (Sow.) (Britain and U.S. America). This 

 forms elongated brown spore-patches on the leaves of various 

 species of Glyceria. Brefeld states that the smooth spherical 

 spores germinate in water, and give off a short unicellular 

 promycelium which undergoes no further development. In 

 nutritive solutions the spores germinate in like manner, but 

 the promycelium becomes thread-like and septate, and gives 

 off conidia laterally ; new promycelia continue to be given 

 off from a cell which remains behind inside the spore, and the 

 conidia ultimately develop into hyphae. 



Ust. hypodjrtes (Schlecht). This species forms dark smutty 

 coatings on haulms and leaf-sheaths of Glyceria Jluitans, Dip- 

 lachnis fusca, Agropyrum repens, Galamagrostis epigea, Psamma 

 arenaria, Stipa pennata and S. capillaris, Bromus erectus, Triticum 

 repens and T. vulgare, Mymus arenariiis, Panicum repens, Phrag- 

 mites communis, Arundinaria, etc. The spores are brown, 

 smooth-walled, and irregularly spherical or quadrangular ; they 

 germinate in water or nutritive solutions, producing mycelia 

 direct, without previous formation of conidia. 



