172 MUTATION. 



have resulted from a faulty technique, and the presence of pol- 

 len on the stigmas. The fact that only certain combinations 

 would produce good seed from unfertilized female flowers con- 

 siderably narrowed the range of our crosses. In 1914 the seed 

 of three non-fert51ized hybrids was sown. We expected either 

 of two things, apogamy, production of seeds by some asexual 

 process, from cells not identical with real fertilizable ovules 

 or real parthenogenesis, the spontaneous development of real, 

 fertilizable ovules into seeds. In the first case we would have 

 obtained a descendant which reproduced the mother- tj^pe, the 

 characters of the hybrids, and in the case of real parthenoge- 

 nesis wee xpected to see a Mendelian segregation, the segregation 

 of genes over the gametes of a heterozygote. The latter altern- 

 ative possibility proved to be the case. The cross between 

 Miracle and Vegetable-marrow may be cited as one of the clear- 

 est instances. Vegetable-marrow has long, narrow fruits, with 

 perceptible ribs. The fruit has a hard shell which is white, and 

 turns bright yellow on ripening. The seeds are normal. Miracle 

 has fruits which are very much heavier, roundish-oval in shape, 

 flattened at both poles. There are no ribs, and the colour is 

 dark green, marbled with yellow stripes. The fruit has a very 

 soft sheU, which even in ripe fruit can be pierced with the 

 finger, and the seeds lack the seed-coat, the cotyledons being 

 naked. 



The hybrids had oblong fruit, shorter than Vegetable-mar- 

 row, but not as round as Miracle. The colour was green mar- 

 bled, with yellow stripes. Ribs were absent. The skin was hard, 

 and the seeds were all covered with normal hard seed-coats. 

 Both reciprocal hybrids presented the same combination of 

 parental charcters. 



Among the plants raised from unfertilized ovules, only twelve 

 were grown until they produced ripe fruit. Of these, seven 

 bore green fruit, more or less marbled, four whitish yellow, and 

 one orange with yellow stripes. Five of them showed ribs, and 

 seven had a smooth top. Four of the plants gave fruit with 

 naked seeds, and the other eight had seeds with seed-coats. 



