THE RUNTS OF NOVA SCOTJA. FRASEH. 329 



Blackman found that the aecial stroma formed taiieath the 

 epidermis consisted of small cells about three cells deep. The 

 upper cells divide by walls parallel with the leaf surface. 

 The upper cells thus formed are sterile. The lower cells formed 

 by this division are fertile and have a large nucleus. Each 

 cell elongates and soon two nuclei are seen in the cell, one of 

 these having migrated into the fertile cell from the mycelial 

 cell directly beneath or at the side of the base. A minute 

 pref oration is made in the wall and the nucleus migrates 

 through. These nuclei divide side by side forming four 

 nuclei, a wall separates the pair and the end cell forms the first 

 spore. Conjugate division continues in such a way as to form 

 a long row of cells each having two nuclei. Each cell does not 

 at once form a spore but conjugate division of the nucleus takes 

 place again, and a small cell is cut off from below, thus form- 

 ing the spore and the intercalary cell. This migration and 

 association of the nuclei is regarded as sexual fusion. This 

 marks the beginning of the binucleated condition of the sporo- 

 phyte generation. The unnucleated stage, on the other hand, 

 from the basidiospores up to the base of the aecium, constitutes 

 the gametophyte generation. Blackman regards the process 

 as of the oosporic type "a female cell is fertilized by the 

 nucleus of an ordinary vegetative cell. 7 ' 



Blackman regards the sterile apical of the female gamete 

 as homologous with the trichogyne of some other plants, and 

 suggests that it once pushed its way through the epidermis, and 

 functioned as a trichogyne fusing with the spermatia. He 

 regards the spermatia as male cells that have lost their function, 

 a simpler "internal" fertilization having replaced the former 

 "external" fertilization. 



Christman described a process of fertilization by the fusion 

 of two cells, but the two cells he found to be approximately 

 equal, so that the fusion is of the zygosporic type, the con- 

 jugation of two equal gametes. 



