GENERAL SUMMARY 377 



Imperfectus being provided with a small pore seems to lie in this : that 

 (1) the pore permits of protoplasm passing readily out of one cell into the 

 next and thus being moved to places where it is needed, while (2) the 

 pore, being very small, can be closed instantaneously when one of the 

 cells adjacent to it is killed or dies. 



The time taken for the formation of a septum as an annular ingrowth 

 from the lateral wall of a hypha was found to be : in Rhizopus nigricans, 

 20-25 minutes ; in Rhizoctonia solani, about 10 minutes ; and in a Ciboria 

 which grows on male Birch catkins, about 6 minutes. 



Newly-formed septa in the mycelium of Rhizoctonia solani and of the 

 Ciboria that grows on male Birch catkins bulge forward temporarily 

 toward the growing-point, and sometimes, in R. solani, in a single hypha, 

 a series of 2-5 of the last-formed septa bulge forward. Through the pore 

 of a bulged septum protoplasm is streaming toward the growing-point 

 of the hypha. The phenomenon of bulged septa affords evidence that, 

 in a hypha, several cells behind the growing-point are manufacturing 

 protoplasm and are constantly pressing it forwards toward the growing- 

 point, thus enabling the latter to extend the hypha rapidly in length. 



It is suggested that, in the Hymenomycetes, e.g. Coprinus lagopus, 

 when a haploid mycelium is being diploidised by nuclei derived from 

 a mycelium of the opposite sex, the invading nuclei travel through the 

 mycelium from cell to cell via the open pores in the middle of the septa 

 and that, contrary to the views of Lehfeldt, the cross- walls do not become 

 broken down. 



PART II 



Chapter I. — The history of our knowledge of the Sporobolomycetes 

 has been reviewed. The group, according to Derx, contains two genera, 

 Sporobolomyces and Bullera. 



The species of Sporobolomyces chosen for study by the author was 

 S. roseus. 



In their asymmetrical development at the end of an aerial conical 

 sterigma and in their drop-excretion mode of discharge, the spores of 

 Sporobolomyces roseus exactly resemble (1) the basidiospores of the 

 Hymenomycetes and the Uredineae, and (2) the secondary conidia, 

 regarded by the author as the true basidiospores, of such Tilletiaceae as 

 Tilletia and Entyloma. 



In Sporobolomyces roseus growing on a culture medium, as was 

 determined by continuous watching, a single sterigma may develop two, 

 three, or possibly more spores in succession. This does not occur in the 

 Hymenomycetes, the Uredineae, or the Tilletiaceae. 



A yeast cell of Sporobolomyces roseus, when growing in a culture 

 medium, may produce (1) a single sterigma or (2) two or three sterigmata 

 in succession. When a single sterigma is produced, two, three, or possibly 



