CULTIVATION AND GROWTH 



Figure 1. The growth of Fusarium solani in an aerated medium. Open circles, 

 dry weight; closed circles, optical density. 



to Streptomyces fradiae delays the onset of the autolytic phase (132). 



The growth rate varies not only between species, but between differ- 

 ent isolates or clones of the same species; this has been found to be 

 true in both liquid and agar cultures (71, 88, 89, 130). 



The first phase, that of no apparent growth, presumably has two 

 components: a genuine lag phase before spore germination, and a 

 phase in which growth is occurring but is undetectable by the methods 

 used. The details of this growth period have not been studied in the 

 fungi. In bacteria it appears that growth, as measured by protein and 

 nucleic acid synthesis, begins immediately, with no true lag period 

 (298). 



The second phase is that of rapid growth. As Emerson (86) has 

 shown, the cube root of the dry weight increases linearly with time over 

 a major portion of the period (Figure 2). It should be stressed, how- 

 ever, that this relation holds only if no external factor, e.g., oxygen or 

 nutrient concentration, is limiting to growth. Conversely, a curve con- 

 forming to that of Figure 2 indicates that the organism is growing un- 

 restrictedly. 



The morphological basis of mycelial development is that growth 



