SPORULATION 321 



of feedings upon the time of fruiting. The protoplasm continued to 

 grow as long as there was abundant food, but when the food was 

 exhausted, the sHme mold passed into the fruiting stage. 



Leonian (1923, 1924) used a technique in studying sporulation which 

 consisted in growing a fungus in a medium suitable for vigorous vegetative 

 growth, and then transferring it to solutions of different concentrations 

 to stimulate sporulation. When sterile mycelium of Valsa leucostoma 

 was transferred from a medium containing 1.5 per cent nutrients to a 

 medium containing 0.37 per cent nutrients the ratio of perithecia to 

 pycnidia increased. Transferring sterile mycelium to more concentrated 

 nutrient solutions favored the production of pycnidia and decreased the 

 number of perithecia formed. Endothia 'parasitica showed a decrease in 

 the number of pycnidia when the mycelium was transferred from a weak 

 to a concentrated medium. When the sterile mycelium was grown in a 

 concentrated medium and transferred to distilled water, the pycnidia 

 did not mature but an enormous number of pycnidium initials were 

 formed. If such a culture were then transferred back to a concentrated 

 medium, maximum sporulation was obtained. A review of the literature 

 on the effect of concentration on fruiting is given by Leonian (1924). 



From the above examples we may conclude that the concentration of 

 nutrients in a medium may have a profound influence upon fruiting, and 

 that the different types of fruiting (sexual and asexual) may have different 

 requirements. Not only the amounts of the different nutrients but the 

 proper balance between the components of the medium may be essential 

 for maximum sporulation. 



Nitrogen source. The source of nitrogen influenced the formation of 

 pycnidia and spores by Phyllosticta solitaria (Mix, 1933). The specificity 

 of the nitrogen source was greater for the production of spores than for the 

 formation of pycnidia. The different isolates of this fungus responded 

 differently to the various nitrogen sources. Nitrate nitrogen was the 

 most favorable. This may have been due to an indirect effect on the pH 

 of the medium, for this fungus sporulates only between pH 4.2 and 5.8. 



In our laboratory we have observed that sporulation of some fungi is 

 favored by certain sources of nitrogen, which are not necessarily the same 

 as those which are favorable for growth (Fig. 64) . A few of these species 

 with the more favorable nitrogen sources for sporulation are Monilinia 

 fructicola, ammonium tartrate, glycine; Phoma betae, glycine; Neo- 

 cosmopara vasinfeda, glutamic acid, glycine; Septoria nodorum, glycine; 

 Diaporthe phaseolorum var. batatatis, asparagine; Choanephora cucur- 

 bitarum, organic nitrogen. 



Carbon source. Not all carbon sources are equally suitable for fruit- 

 ing of fungi. Some which are favorable for mycelial growth do not favor 

 sporulation. Hawker (1939) found the number of perithecia produced 



