602 



COMPARATIVE MORPHOLOGY OF FUNGI 



migrate into the other but the copulation tubes take up the contents of 

 both cells and develop to sprout mycelia. 



In other species, as U. nuda (Rawitscher, 1922), U. Tritici (Lang, 1910; 

 Paravicini, 1917) and U. Hordei (Hils, 1912), the promycelium, under 

 suitable conditions of growth, i.e., in presence of high oxygen tension, 

 may develop mostly to unbranched hyphae instead of sprout mycelium. 

 Occasionally these hyphae can again change to sprout mycelium. 

 Between two more or less neighboring hyphal cells or between two hyphae 

 of different promycelia, there appear copulation tubes through which 

 the content of one cell wanders over into that of the other. 



Fig. 397. — Ustilago levis. 1. Portion of intercellular hypha. Ustilago nuda. 2 to 5. 

 Germinating and copulating promycelia. Cintractia Montagnei. 6, 7. Germinating and 

 copulating promycelia. Ustilago Tragopogonis pratensis. 8. Young binucleate spore 

 fundaments. 9. Mature uninucleate spores. Ustilago Holostei. 10. Germination of 

 smut spore with fusing sporidia. Ustilago domestica. 11. Germination of smut spore in 

 nutrient solution. Ustilago Panici-frumentacei. 12. Submersed germination of smut 

 spore. 13. Germination of smut spore in air. (1 X 860; 2 to 9 X 660; 10 to 13 X 240; 

 after Lutman, 1910; Rawitscher, 1912, 1922; and Brefeld, 1895.) 



In U. bromivora (Bauch, 1925), as in Cintractia Montagnei, copulation 

 may occur between two promycelial cells through copulation tubes or, as 

 in U. violacea, between two ordinary sprout cells; in certain strains the 

 sprout cells, as in the promycelial cells of U. nuda, develop first to long 

 copulation tubes which only fuse at the tip. U. bromivora shows an 

 interesting retrogression in the form of its promycelium. Besides the 

 normal four-celled promycelium, there may also develop from a smut 

 spore, two two-celled or one two-celled and two one-celled or one one- 

 celled and one three-celled promycelium. The number four of the pro- 

 mycelial cells generally remains constant, while the promycelium has 

 entirely lost its characteristic form. 



