244 THE AMERICAN NATURALIST. [VoL. XXXIX. 



ter, is considered by Oltmanns ('98b) to have nutritive relations 

 alone. Oltmanns studied the fusion with auxiliary cells in sev- 

 eral genera, but especially for Callithamnion and Dudresnaya, 

 and is satisfied that the cell unions concern only the cytoplasm. 

 Fertilization takes place with the fusion of gamete nuclei in 

 the carpogonia and these cells develop the sporophyte genera- 

 tions. The fusion of fertilized carpogonia or filaments derived 

 from them with auxiliary cells, is a feature of a sort of semipara- 

 sitic relation that the sporophyte holds to the gametophyte by 

 which it is nourished in part through organic connections with 

 the gametophyte. The nuclei of the sporophytic structures 

 remain quite apart from those of the auxiliary cells so that the 

 union is purely cytoplasmic. This theory of Oltmanns has 

 received strong support through the detailed nuclear studies of 

 Wolfe (: 04) on fertilization and the development of the cysto- 

 carp of Nemalion who finds cytological evidence of the sporo- 

 phytic character of the cystocarp. These papers of Oltmanns 

 and Wolfe have been discussed by myself in the Bot. Gas., vol. 

 27, p. 314, 1899, and vol. 39, p. 64, 1905. 



Writers have at times attached sexual significance to the con- 

 spicuous fusions between sporidia of certain of the Ustilaginales 

 (e. g., Tilletia). But there seems at present no reason to regard 

 this phenomenon as different from the cytoplasmic connections 

 frequently established between cells of hyphae which are ulti- 

 mately associated in a common mycelium where the whole 

 forms a close unit with respect to common nutritive relations. 

 Such protoplasmic connections were treated in the first part of 

 this section. Harper ('99a) studied the union of conidia and 

 cells of the promycelium in Ustilago and concluded that the 

 fusions involve the cytoplasm alone, there being no nuclear 

 changes. However, Federley (: 03-: 04 ; review in Bot. Zeit., 

 vol. 62, p. 171, 1904) has observed the migration of a nucleus 

 from one conidium to another in Ustilago tragopogonis pratensis 

 (Pers.), and a fusion within the latter. This nuclear fusion was 

 not found in some other forms of Ustilago which behaved as 

 Harper has described. There is nothing in the morphology of 

 the conidia to indicate that they are sexual cells and from what 

 we know of the life history of Basidiomycetes we should look 



