214 PLANT DISEASES 



of these parts is diseased. On the leaf the first evidence 

 of disease is the appearance of whitish wrinkled blisters, 

 usually surrounded by a reddish tinge of colour; at a later 

 stage the blisters burst and expose the mass of spores. 

 On the ear large, whitish, polished swellings appear, 

 reaching in size that of a walnut, and Brefeld states that 

 in an artificially infected ear the swelling reached the size 

 of a child's head. As the spores mature the swellings 

 become darker in colour, and the enclosing membrane 

 finally ruptures, exposing the dark olive-green mass of 

 spores. 



The spores germinate readily at maturity, and produce 

 numerous very minute secondary spores; and it is mostly 

 by means of these secondary spores that the disease 

 spreads so rapidly, inoculation taking place in the first 

 instance from spores that have remained over year 

 in the soil, or from secondary spores that have con- 

 tinued to propagate themselves by germination. Unlike 

 most other cereals, maize can be inoculated at any age, 

 so long as young growing tissue is present at any point. 



Preventive Means. — It has been observed that smut 

 is most abundant where fresh manure has been used, 

 the spores probably germinating in the manure, and the 

 secondary spores continuing to reproduce themselves until 

 the maize is susceptible of infection. 



Brefeld, Uniers. aus dem Gesammtgebieie der MykoL, 

 Hefte iv., xi., numerous figs. 



Norton, Kansas State Agric. Coll., Bull. No. 62, 10 pi. 



Ustilago hordei, Jensen. — Attacks ears of cultivated 

 barley; the spore-mass is very hard and persistent, being 



