456 



BOTANY 



PART II 



berry, and has been fully investigated by BLACKMAN ( 78 ), the hyphae beneath the 

 epidermis when about to give rise to an aecidium first cut off a sterile cell, which 

 undergoes no further development, from their ends (Fig. 406 A}. The cell below 

 this increases in size ; it has at first>only a single nucleus, but becomes binucleate 



2 



FIG. 403. Puccinia graminis. 1, Transverse section through a grass-haulin with group of teleuto- 

 spores. 2, Germinating teleutospore with two basidia. 3, Vegetative, It, germinating basidio- 

 spore ; the latter has formed a secondary spore, not having been able to infect a host plant. 

 5, A portion of a group of uredospores (u) and teleutospores (t) ; p, the germ-pores. 6, Germinat- 

 ing uredospore. (1, 2, 8, U after TULASNE ; 5, 6 after DE BABY. 1 x 150 ; % x circa 230 ; 

 3, k X 370 ; 5 x 300 ; 6 x 390. From v. TAVEL, Pilze.) 



by the passage of a nucleus into it from an adjoining mycelial cell. The two 

 nuclei do not fuse. The binucleate cell undergoes successive divisions into a chain 

 of spore-mother-cells, each of which has a pair of nuclei ; and from each spore- 

 mother-cell an upper binucleate aecidiospore and a sterile intercalary cell, which 

 is also binucleate but soon shrivels up, are derived by a transverse division (B, C}. 

 According to CHRISTMAN ( 78 ) the development of the aecidiospores in Phrag- 

 midium speciosum (Fig. 407), which is parasitic on Rosa, proceeds somewhat 



