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TECHNICAL BULLETIN 4. 



mount is made the hyphse appear in segments as represented in the figure. 

 At this early stage thej^ show no constrictions at the septa. No conidia 

 can be found. Clamp connections have not been observed. 



If, however, cultures several weeks old are examined microscopically it 

 will be observed that certain changes have taken place. The aerial myce- 

 lium may remain about the same as described, except that the cells appear 

 vacuolated, but there will now be found a different kind of mycelium be- 

 neath the agar surface. These hyphse are stouter, averaging S.2fi in diam- 



Fia. 2. — Details of hyphse in culture. Detached hyphal cells at C and further development 



of same at D. 



eter, the cells are much shorter, the septa very distinct, and the hj^phae 

 decidedly constricted at the septa, so much so that the hyphse appear almost 

 like strings of separate cells. A large proportion of the cells become shaped 

 like dumb bells. When disturbed, as in mounting, the cells of the thread 

 break apart very readily so that when one makes a mount of an old luxuri- 

 ant culture, such as on onion agar, he hardly finds mycelium at all, but 

 only these irregular separate units. IVIost of them are branched at the 

 tip. A strand of this mycelium is represented in Fig. 2, B, with a young 

 ordinarj'' hypha for comparison. The appearance of the separate cells 

 from an onion agar culture as seen floating about in the microscopic prep- 

 aration is represented in Fig. 2, C. 



Fate and Fuvdion of the Detached Hyphal Cells. 

 Since these large detached cells appear so early in the development of a 

 culture and in such large numbers, it does not seem probable that they 

 represent merely a stage in the degeneration or breaking down of the 

 mycelium. Apparently they have some role in the life history of the 

 organism. In order to determine whether they are capable of further de- 

 velopment, a culture was thoroughly shaken in water and the detached cells 

 floated out on sterile agar plates as described previously for germination of 



