138 SCIENCE PROGRESS 



owing to the prevalence of smut. The appearance of a smutty 

 oat plant is well known. When the disease is most advanced 

 the oat grain, first converted into a black powder, is completely 

 destroyed, and the powder — the smut spores — are dispersed, 

 leaving of the original flowering panicle merely a skeleton. Such 

 smutty ears do not tell the whole story of the loss ; there are 

 many heads not present at all, because, in a still earlier stage 

 of disease, the oat plants have been killed off by the smut or the 

 oat grains have failed to sprout because of it. 



As late as the middle of the eighteenth century the black 

 powdery substance of the grain was regarded as part of the 

 corn plant itself — a degeneration of the substance of the grain, 

 deposited by a change in the juices of the grain, and called 

 " vitium, morbus, et pestis." 



In the middle of last century the brothers Tulasne published 

 a beautifully illustrated account of their investigations of the 

 rusts and smuts, and showed how closely allied the two forms 

 of fungi responsible for these diseases are. They showed 

 that in each case the resting spore (teleutospore or teleuto- 

 gonidium of the rust, chlamydospore of the smut) on germination 

 produces a short filament, jointed or unjointed, and that from 

 ■each joint a secondary spore arises. When the filament is 

 unjointed, then the secondary spores arise from its apex or free 

 end as a rosette. The thread, jointed or unjointed, arising from 

 the resting spore has been called the promycelium, and the 

 secondary spores or conidia arising on this promycelium the 

 sporidia. It is only within quite recent years that the affinities 

 of the rusts and smuts to the mushroom, toadstool, and puff- 

 ball group — the Basidiomycetes — have been emphasised. The 

 promycelium of Tulasne is now called a hemi-basidium. The 

 rust and smut (Ustilago) jointed promycelium has its counter- 

 part in the jointed basidium of the Proto-Basidiomycetes, and 

 the unjointed promycelium of the bunt {Tillctia) has its counter- 

 part in the basidium group of the ordinary mushroom group, 

 the Auto-Basidiomycetes. 



The rust or smut sporidium is the homologue of the 

 basidiospore or basidiogonidium of the mushroom, and the 

 rusts and smuts are now called the Hemibasidii. Where close 

 homologues in the superstructure or after-development are 

 indicated the foundations should be sure and distinct. The 

 teleutospores of rust and the chlamydospores of smut are 



