A simple way to demonstrate sexual reproduction in 

 the bakery mold, Neurospora 



B. O. Dodge and Marjorie E. Swift 



The gardener propagates his plants either by cuttings of 

 some sort, or by seeds. The development of a seed usually re- 

 quires that the egg in the ovule be fertilized. On this account 

 the biologist refers to the formation of a seed as due to sexual 

 reproduction, in contrast to asexual reproduction where new 

 plants arise directly from buds developed from leaf, stem, or 

 root. 



The fungi are very low forms of plant life, nevertheless they 

 follow much the same laws of reproduction and inheritance that 

 govern these processes in the higher plants. Fungi reproduce 

 themselves asexually by means of spores of various sorts de- 

 veloped as natural cuttings from the vegetative growth. No act 

 of fertilization is then involved. A square inch of the blue mold 

 found on decaying lemons probably develops a billion or more 

 of these spore cuttings, which serve to propagate the fungus very 

 effectively from month to month and year to year. Sooner or 

 later the fungus will reproduce itself sexually. This does in- 

 volve an act of fertilization where two nuclei from different 

 cells unite in a fusion. This stage is sometimes very difficult 

 to discover and difficult to demonstrate in culture, once it is 

 known to occur. 



In an article published in Torreya, 30: 35-39, 1930, there 

 was given a short description of experiments with material 

 which could be used by teachers of biology and botany to 

 demonstrate sexual reproduction in the orange-colored bakery 

 mold, Neurospora sitophila, which belongs to the class Ascomy- 

 cetes. It was shown that a single spore culture of this fungus 

 cannot produce ascocarpic fruit bodies by itself. Such strains 

 are unisexual just as are strains of the common bread mold, 

 Rhizopus, a fungus used by teachers to demonstrate sexual re- 

 production in the Phycomycetes. It is necessary to grow my- 

 celia of opposite sex together in the same culture in order to 

 obtain the sexually produced fruit bodies. Therefore, when two 

 mycelia of opposite sex of the Neurospora bakery mold are 



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