DIRECTION OF MOVEMENT OF NUCLEI 231 



mycelium had developed diploid hyphae on the half nearest to the 

 inoculum and haploid hyphae on the half oj^posite thereto ; (2) the 

 outer (distal) ends of all the radial pieces of mycelium had developed 

 diploid hyphae ; and (3) the inner ends of all the radial pieces of 

 mycelium had developed haploid hyphae only, excepting that of 

 the piece containing the inoculum which had developed diploid 

 hyphae only and that of one piece next to the piece containing the 

 inoculum which piece had developed both haploid and diploid 

 hyphae (Fig. 130). 



From the observations just recorded for Experiment No. 1 we 

 may conclude that, when a large mycelium, through the action of 

 a minute peripheral inoculum, has just become completely diploi- 

 dised in its peripheral zone (all the hyphae there having clamp- 

 connexions), there are many hyi^hae in the central part of the 

 mycehum still in the haploid condition but that, toward the centre, 

 proceeding from the inoculum, there are a number of hyphae which 

 have become diploidised. 



The observations made in connexion with Experiment No. 1 

 also seem to indicate that the nuclei derived from a tiny peripheral 

 inoculum travel through a large haploid mycelium more readily in 

 a circle through its younger exterior portions than directly through 

 its older interior portions. 



Experiment No. 2. A large haploid mycehum {AB) was grown 

 on dung-agar in a large Petri dish until it had attained a diameter 

 of 6-1 cm., and then there was removed from it (together with the 

 agar below) a central portion 3 • 8 cm. in diameter. Thus there was 

 left in the Petri dish a large hollow ring of mycehum about 1 • 1 cm, 

 wide. This large mycelial ring was now inoculated at one spot on 

 its outer periphery with a tiny fragment of a haploid mycelium 

 {ab), as shown in Fig. 131. 



Six days after inoculation, the large hollow ring of mycehum 

 had become diploidised all around its outer margin. 



From the results of Experiment No. 2, as just recorded, we may 

 conclude that, when a large haploid mycelium is becoming diploi- 

 dised by nuclei derived from a small peripheral inoculum, the nuclei 

 can travel tangentially all around an outer zone of the mycelium. 



It may be added that the experiment just described provides 



