On a New Species of Melanotaenium. Rudolph Beer. 339 



starting-point for a more complete account when more abundant 

 material becomes available. 



With regard to the nucleus of Ustilagineae the following is a 

 summary of work already carried out. The earliest paper of im- 

 portance is that by Dangeard (1892). He examined Usiilago 

 Tragopogi, U. Carbo, U. violacea, Doassansia Alismatis, Enty- 

 loma GhiHcii, Uyocystis Violae, and Tilletia Caries, and found 

 that the spore-bearing hyphae and the young spores are always 

 bi-nucleate. 



In 1899 Harper (1899) confirmed Dangeard's results, working 

 on Ustilago Carbo, U . Maydis, U. antherarum, and U. Scabiosae. 

 Federley (1904) for the first time observed a passage of the nu- 

 cleus from one conidium to the other during the conjugation of 

 these bodies in Ustilago Tragopogonis-pratensis Pers. He be- 

 lieved that these nuclei fused at once and that a bi-nucleate 

 stage of the hyphae and spores did not occur in this plant. 



Six years later Lutman (19 10) published the result of his in- 

 vestigations on Ustilago laevis, U. Zeae, Urocystis Anemones, 

 Doassansia Alismatis and Entyloma Nymphaeae. He observed 

 in Ustilago laevis that the conidia are uni-nucleate and that 

 during conjugation the nucleus and most of the cytoplasm of 

 one spore migrate into the other one. The mycelial cells in the 

 host plant were found all to be bi- or multi-nucleate. During 

 the development of the spores the two nuclei fuse so that the 

 mature spore is uni-nucleate. 



In 1912 and 1914 Rawitscher gave an account of the cytology 

 of Ustilago Tragopogonis, U. Maydis and U. Carbo. In U. Tra- 

 gopogonis-pratensis Pers. he found that the hyphae and young 

 spores are bi-nucleate whilst the mature spore is uni-nucleate. 

 The pro-mycelial cells and the conidia are uni-nucleate. In 

 U . Maydis Corda the cells of the hyphae are uni-nucleate until 

 just before spore-formation when the cell contents of two ad- 

 jacent cells become fused with one another through the resorp- 

 tion of the membrane previously separating them from one 

 another. Bi-nucleate spore rudiments are thus established. The 

 two nuclei fuse and uni-nucleate spores result. The conidia are 

 uni-nucleate. 



In the case of U. Carbo it is either the cells of the uni-nucleate 

 mycelium or the uni-nucleate sporidia themselves which may 

 conjugate with one another and give rise to bi-nucleate cells. 

 The young spores are bi-nucleate and the mature ones uni- 

 nucleate. 



In the case of Tilletia Tritici Rawitscher also found that the 

 sporidia copulate in pairs and, upon their germination, give 

 rise to bi-nucleate hyphae. 



Werth and Ludwig (1912) came to very different conclusions 



