14 



the 8o's, it was determined by spore culture that the loose smut of oats' is an entirely different 

 form from the one existing in wheat and barley^. The loose smut of oats, when germinating in 

 nutrient solutions, forms chiefly hemibasidia with conidia, which continue budding indefinitely 

 as long as the nutrient substances of the substrata last. After exhausting the nutrient 

 solutions, the broken down bud conidia grow out into strong, long germinating tubes which 

 were never found in conidia whose spores germinated in water''. The loose smut of wheat and 

 also that of barley germinate with hemibasidia, to which the first conidia formed remain attached, 

 growing out into long germinating tubes, but free conidia never appear. An increase of the 

 fungus through budding of the conidia, which takes place indefinitely in the oat smut, is never 

 oliserved here. Only threads are shown which formed hemibasidia directly. They branch weakly in 

 nutrient solutions and develop only a relative length' The difference between this smut form 

 and that of oats is so convincing that, according to my observations, the loose smut in wheat and 

 in barley must be taken as distinct species. The spores of the loose smut of wheat and barley 

 may not be distinguished from one another. Also no differentiation whatever is shown in the 

 germination of the spores. The question remains open whether the fungus in barley is a still 

 different form from the one in wheat. Anticipating the actual decision, Rostrup has designated 

 the loose smut of wheat as Ustilago tritici, in contrast to barley smut, to which Brefeld had 

 given the name Ustilago hordei. 



After the natural dusting, that is, the infection of the blossom by smut spores, it is abso- 

 lutely necessary that the spore masses in oats, in wheat and in barley, should appear simul- 

 taneously with the blooming of the grain. This takes place in a most striking manner. One can 

 observe indeed that the spore masses of the plants attacked precede somewhat the blossoming 

 of the grain plants, but in any case are present at the time of completest development and are 

 capable of being disseminated, when the blossoms are developed and in full bloom. This 

 peculiar coincidence of the blossoming time of the grain and the ripening of the spore masses 

 of the plants attacked necessarily gives rise to the question, whether any dusting, that is, any 

 infection of the blossoms by smut spores, might have taken place here. And the designation loose 

 smut for this spore mass disseminated by the wind, has already become so significant that one is 

 unconsciously led to consider that there is a natural connection between these smut spores, 

 capable of germination, and an infection of the blossom. 



(1) Compare the text and illustrations in Parts V (plates II and III) and XII (figs. 25-28, plate 

 VII). 



(2) Compare figs. 29-32, plate VII, Part XII. 



(3) 1. c. text and illustrations of Part V. 



