THE CENTROSOME AND THE BLEPHAROPLAST 



81 



cone of fibrils extending toward the chromatin, divides into two which 

 take up positions opposite each other at the nuclear membrane, at which 

 time asters develop in the cytoplasm. Faull (1905) found centrosomes in 

 Hydnobolites, Neotiella, and Sordaria; in the last named genus they 

 appear to be discoid while the cell is in the resting condition but round 

 and smaller during mitosis. In Humaria rutilans Miss Fraser (1908) 

 observed two centrosomes lying near each other, each at the apex of a 

 cone of fibers and surrounded by a faint aster. These move apart and 



FIG. 22. Centrosomes in ascomycetes. 



A-C, Phyllactinia corylea: division of nucleus in ascus, showing behavior of centro- 

 somes. D, Erisiphe cichoracearum: formation of ascopore wall. (After Harper, 1905.) 



establish the spindle in the usual manner. Centrosomes are also figured 

 in Ascobolus and Lachnea by Fraser and Brooks (1909); in Otidea and 

 Peziza by Fraser and Welsford (1908); in Microsphcera by Sands (1907); 

 and in Pyronema by Claussen (1912). 



In the Basidiomycete Boletus (Levine 1913) the centrosomes present 

 during the last mitosis in the basidium attach themselves to the basidium 

 wall, and in close connection with them the daughter nuclei are recon- 

 structed. They mark the points of origin of the sterigmata and eventu- 

 ally pass into the spores. 



