Onygena equina : a Horn- destroying Fungus. 159 



details of development of the asci, their nucleated contents, and the 

 spores are determined. As the spores ripen, the asci, which are 

 extremely evanescent, disappear, and in the ripe sporocarp only spores 

 can be seen lying loose in the meshes of the gleba. The ascomycetous 

 character of the fungus is thus put beyond question, though the 

 peculiar behaviour of the developing ascogenous tufts at one time 

 rendered it questionable whether the older views as to the relationships 

 were not more probable. 



No one had hitherto been able to trace the germination of these 

 ascospores — the only spores known previously — and De Bary ex- 

 pressly stated his failure to do it. The author finds that they require 

 digesting in gastric juice, and so in nature they have to pass through 

 the stomach of- the animal. By using artificial gastric juice, and 

 employing glue and other products of hydrolysis of horn, the details of 

 germination and growth into mycelia, capable of infecting horn, were 

 traced step by step under the microscope and fully described. 



No trace of any morphological structure comparable to sexual organs 

 could be discovered, though many points suggest the alliance of this 

 fungus with Erysiphese and Truffles. 



The author also found that similar digestion promotes the germina- 

 tion of the chlamydospores, and in both cases has not only traced the 

 germination step by step, but has made measurements of the growth 

 of the mycelium, induced the formation of chlamydospores on the 

 mycelium again, and by transferring vigorous young mycelia to thin 

 shavings of horn has observed the infection of the latter. 



It thus becomes evident that the spores of Onygena pass through the 

 body of an animal in nature, and, as might be expected from this, 

 extract of the animal's dung affords a suitable food medinm to re-start 

 the growth on horn. Probably the cattle lick the Onygena spores from 

 their own or each other's hides, hoofs, horns, &c, and this may explain 

 why the fungus is so rarely observed on the living animal : it is recorded 

 from such in at least one case however. 



Very little is known as to the constitution of horn, and some experi- 

 ments have been made to try to answer the question — what changes the 

 fungus brings about. The research has also obvious bearings on the 

 question of the decomposition of hair, horn, feathers, hoofs, &c, used 

 as manure in agriculture. Although a bacterial decomposition of hoof 

 substance is known to the author, special investigation of the question 

 showed that in the present case no symbiosis between bacteria and the 

 Onygena exists. 



For the details as to the literature, the discussion as to the syste- 

 matic position of Onygena, the experimental cultures, growth measure- 

 ments, and the histology, the reader is referred to the full paper, which 

 is illustrated by plates and numerous drawings. 



