390 SPORE GERMINATION 



2. Predominantly multinucleate: Aspergillus echinulatu§ (8), Botry- 

 tis cinerea (128), Helminthosporium sativum (54, 137). Sporangio- 

 spores of Rhizopus nigricans are uninucleate (12), those of Mucor dis- 

 persus multinucleate (68). 



Nuclear condition is of particular importance in genetic studies, since 

 a heterokaryotic mycelium which produces uninucleate conidia — more 

 accurately, conidia from uninucleate conidiophores — essentially regen- 

 erates the parent types in the absence of gene exchange (112). By 

 extension of this principle, it is possible to infer from genetic evidence 

 in Streptomyces spp. that the conidia are uninucleate or arise from 

 uninucleate cells (28). 



The number of nuclei in macroconidia of Neurospora crassa is re- 

 duced by cultivation in a minimal medium (138) or in a sorbose me- 

 dium (5). The nuclei of the higher fungi are, of course, normally 

 haploid; Roper (236) has, however, succeeded in inducing the forma- 

 tion of diploid conidia in Aspergillus nidulans, and camphor treatment 

 of Neurospora crassa induces the formation of possibly diploid cells 

 (243). 



100 2.5 3.3 

 Time, hours 



10 100 



Figure 1. The time course of spore germination (probit scale) in Monilinia 

 fructicola (curves 1) and Alternaria solani (curves 2). Arithmic function of time 

 plotted in A, reciprocal function in B. Redrawn from Wellman and McCallan 

 (299), by permission of the Boyce Thompson Institute for Plant Research, Inc. 



