A SEX-FACTOR ANALYSIS 235 



of a diploid mycelium {Ab)-\-{aB) which had been produced by 

 mating the myceUa No. 1 and No. 9 of Table I. In the course of 

 six days from the time of inoculation the large haploid mycelium 

 (Ab) became progressively diploidised all around its periphery ; 

 and, at the end of that time, all its peripheral radial hyphae dis- 

 played the diploid mode of branching and bore clamp-connexions. 

 A piece of mycelium was now removed from the peripheral zone 

 of the large diploidised haploid mycelium at a place in the zone 

 that was farthest from the inoculum (distance from inoculum about 

 7 cm.), and it was transferred to a wide test-tube (3x1 inches) 

 containing sterilised horse dimg. On this culture medium it grew 

 well and, after about ten days, gave rise to fruit-bodies. These 

 were diploid in appearance, and they produced and liberated spores 

 freely, thus functioning in a diploid manner.^ A spore-deposit was 

 obtained from one of the fruit-bodies and a number of the spores 

 were sown singly in dung-agar, and thus nine monosporous mycelia 

 were obtained. 



The nine monosporous mycelia were now paired with one 

 another in all possible ways, with the result that, as shown in 

 Table III, they proved to be divisible into the usual four groups : 

 (AB), (ah), (Ab), and (aB). The Table III was constructed in the 

 same way as Table I and, here again, a ( + ) sign indicates that 

 clamp-connexions were produced and a ( — ) sign that they were 

 not. 



We thus find that the diploidised haploid mycelium produced 

 by inoculating a large haploid mycelium (Ab) with a tiny fragment 

 of a diploid mycehum {Ab)-\-{aB) yielded a fruit-body which 

 liberated all the four possible kinds of spores (AB), {ab), (Ab), and 

 {aB). From this we are justified in concluding that the fruit-body 

 derived from the diploidised originally-haploid mycelium was truly 



^ Hanna (" Sexual Stability in Monosporous Mycelia of Coprinus lagopus,'^ 

 Annals of Botany, vol. xlii, 1928, p. 385), working on Coprinus lagopus in my 

 laboratory, made the following observations: " As a general rule, diploid fruit- 

 bodies are more vigorous than haploid. Many haploid fruit-bodies do not elongate 

 their stipes, or do not open their pilei, or do not produce any spores ; and . . . the 

 most highly developed haploid fruit-bodies produce but relatively few spores, so 

 that their pilei are pale in colour." The pilei of diploid fruit -bodies, when mature, 

 are black in appearance owing to the large number of spores borne on the gills. 



