94 BOTANICAL GAZETTE [august 



number of chromosomes in the higher plants^ has its beginning in the 

 cell produced by the fusion of two gametes — the fusion cell. This 

 cell produces a more or less elongated outgrowth which has been long 

 known as the ^^basidium," and has been often figured and fully 

 described. For obvious reasons, that BLACKMANhas pointed out, the 

 term basal cell is to be preferred to the old term basidium. This cell 

 now produces spores, being a generative cell. The spores may be 

 borne in chains, as has been so often described for the true aecidia, or 

 they may be produced by a process of budding and so be borne on 

 stalks, as I found to be the case in the primary uredosori (figs. i8y ig). 



The spores produced by this first basal cell may infect the same 

 host upon which the gametophyte is parasitic, or they may infect 

 some other host and produce there a sporophyte mycelium. After a 

 period of development this mycelium fruits. When spores are to be 

 produced, large binucleated cells — the basal cells — in all essentials 

 like the cells upon w^hich the aecidiospores and primary uredospores 

 are borne, again appear, this time upon the ends of the binucleated 

 hyphae w^hich mass together beneath the epidermis to form the uredo- 

 sorus. By a process of cell division above described the uredospores 

 are formed. These uredospores may be borne in rows and sepa- 

 rated by intercalar}' cells, as in the case of Coleosporium, or they may 

 be borne upon stalks, as described above for Phragmidium poten- 

 tillae canadensis. The uredospores may reinfect the same host or hosts 

 and repeat this generation an almost indefinite number of times, as 

 is commonly supposed to be the case in Puccinia riihigo-vera. 



Usually, after a few generations of uredospores have been pro- 

 duced, the binucleated mycelium bears the teleutospores which are to 

 end the sporophytic phase in the life-cycle. When teleutospores are 

 about to form, end cells of the hyphae again return to the condition of 

 the large basal cell, and the teleutospores are budded off exactly as are 

 the primary and secondary uredospores. At present we know of 

 only one form in which the teleutospores are borne in chains and 

 separated by intercalary cells. Aaother approach to this condition 

 is perhaps found in the sessile teleutospore of IMelampsora and 

 Coleosporium. The teleutospores of the different genera are only 



i 



secondarily characterized by being made up of one to several cells. 

 The bearing of these facts upon the problems of classification 



