32 



grown from opposite sides in a petri dish culture, many black 

 ascocarps are developed. Very frequently, the ascocarps are dis- 

 tributed over the area occupied by only one of the strains as 

 figured in the article referred to above. 



The orange-colored conidia characteristic of Neurospora 

 have always been assumed to function only as asexual spores in 

 vegetative reproduction. It has been discovered, however, that 

 these monilioid conidia have another and quite different func- 

 tion in fertilization; that is, they may also function "sexually." 

 This discovery provides the biology teacher with another and 

 much easier method of demonstrating sexual reproduction in 

 Ascomycetes. 



It is only necessary to grow one of the unisexual strains in a 

 petri dish culture, and then apply a spore suspension of the 

 conidia from a mycelium of the other sex to any particular spot 

 on the plate culture. This can be done by means of a capillary 

 tube or fine pipette, or a fine water color brush. When one puts 

 pollen on the receptive stigma of a flower we call this act pol- 

 linating. Therefore, when one places the conidia of the bakery 

 mold on the receptive organs developed on the mycelium we 

 may refer to the act itself as conidiating. 1 Within twenty-four 

 hours after conidiating the receptive bodies one can see exactly 

 where fertilization has taken place, resulting in the rapid forma- 

 tion of the ascocarpic fruit bodies. With a hand lens or low 

 power dissecting microscope, the student can readily distinguish 

 individual ascocarps, such as were shown in figure 2, page 38, 

 of the article in Torreya referred to above. Perithecia (asco- 

 carps) are produced only where the conidia come in contact with 

 the receptive bodies of which there will be thousands scattered 

 all over the culture ready to be fertilized. Figure 1 shows a 

 photograph of a plate culture where the fertilizing conidia were 

 originally applied as though one were printing the letters with 

 invisible ink. The receptive bodies that were not fertilized are 

 not visible in this picture except perhaps showing as a fine pow- 

 der at the center of the culture. The young ascocarps, however, 

 were readily visible 24 hours after the conidia were applied. 



Curiously enough the conidia from the culture producing the 

 receptive bodies will not bring about fertilization when applied 



1 The writers are indebted to Dr. H. A. Gleason for suggesting this very 

 descriptive term "conidiate." You pollinate why not conidiate? 



