ORANGE PLANT ORDINARY COLORLESS RESISTANT SP0RAN6IAL LATE COLORLESS 

 (thln-wolled) PLANT.lthIn wolled) PLANT.tbrown.thIcK v»all«d, PLANT,(thln 



=7/>:^ 



7.5 



12.5 



\ i 



0.5 



99.0 



38 34 



I \ 



No 



No 



I I 



pitted.) 



MEDIUM 



P • 

 2 0»C. 



%P^ 



Yes 



No 



Ava.# gamma" 

 particles per 

 spore in plant. 



Ave.'/, of first 



generation 



population. 



Ave. generation 

 time, hours. 



Melanin In wall 7 



Carotene In 

 protoplost ' 



walled) 



im 



12.5 



15.5 



I I 



less than 



0.1 

 (usually zero) 



108 



0.5 



I 



38 



I \ 



Yes 



No 



I \ 



Yes No 



Fig, 18. 



The four alternate pathways of development in Blastocladiella emersonii. (Fig. 2, Cantlno, 

 In "11th Symp. of the Soc. for Gen. Microbiol.," 1961; reproduced with permission of the 

 Society for General Microbiology.) 



CANTINO: Well, this will be pure guess- 

 work; my working hypothesis is that it is syn- 

 thesized on ribosomal particles close to the 

 membranes near the wall. 



FERGUS: To go back to a former question, 

 if you sample a number of individual sporangia, 

 would you still get this ratio of the four types 

 within a single sporangium? 



CANTINO: Yes, provided the environment 

 is favorable. One can alter these ratios quite 

 easily by modification of the media. For ex- 

 ample, 60% of the spores in a population can be 

 induced to produce orange cells if a suitable 

 concentration of actidione is added (note added 

 in proof: - and if peptone, which tends to repress 



genesis of orange cells, is not present). On the 

 other hand, addition of diphenylamine eliminates 

 orange cells from a population. 



GROSS: These data that you've been discus- 

 sing about the population that can result from 

 germinating spores suggest to me that you're 

 thinking about the mechanism of this differentia- 

 tive process, probably, the way Barbara Wright 

 was thinking about hers. That is this (and tell 

 me if I'm doing either of you an injustice): I 

 have the feeling you are thinking of this as a 

 modulation process. The enzymatic systems 

 that control the product, giving a physically 

 different kind of cell, are all there. What's 

 really critical is that the levels of interaction 



162 



