9 o TEXT-BOOK OF FUNGI 



uredospores and teleutospores having paired nuclei, 

 with four chromatin masses on division. The change from 

 gametophyte to sporophyte occurs in the aecidium, and the 

 transition from sporophyte to gametophyte in the teleuto- 

 spore. 



It has already been stated that Blackman observed what 

 he considers to represent a reduced form of trichogyne 

 present in the aecidium. This organ is represented by 

 what has been here spoken of as the sterile terminal cell, 

 surmounting the fertile cell in the aecidium. The spermatia 

 are considered as male organs, at present functionless. 

 The presence of these rudimentary organs is considered 

 as indicating an affinity between the Uredineae and the 

 Florideae. 



Following Blackman, Christman, an American investi- 

 gator, has paid special attention to what he terms sexual 

 reproduction in the rusts. The species investigated were 

 Phragmidium speciosum and Cacoma niiens. Blackman's 

 observations are, on the whole, corroborated, and the 

 author states his opinion that the discoveries made estab- 

 lish the existence of true sexual cell fusions in the rusts, 

 and that the fusion of nuclei in the. teleutospore is not of 

 a sexual nature, but has wholly to do with the reduction of 

 the number of chromosomes. The behaviour of what 

 Blackman terms the fertile cells in a sorus, that are com- 

 pacted vertically to the surface of the leaf, is as follows. 

 These approach in pairs until portions of two contiguous 

 walls are in contact, and at this point of contact a pore is 

 formed by the solution of the cell-walls, and the protoplasts 

 are brought into contact. The two nuclei pass to the 

 apical portion of the conjugated cell and divide simulta- 

 neously. Two of the daughter-nuclei return to the base of 



