MUTATION. 173 



Most of the plants bore oval fruit, and there was no plant 

 which reproduced the exact shape of either grand-parent. Two 

 of the plants had decidedly pear-shaped fruit, two had almost 

 globular fruit, and the plant with the orange fuit happened to 

 have very long fruits, which may have differed in shape from 

 Vegetable-marrow, mainly because they were soft-shelled. In 

 size there was a great variation in the fruit of the different 

 plants, but as the plants were grown climbing on stands, where- 

 as the original plants and the hybrids were grown straggling 

 on the ground, no fair comparison can be made on this point. 



This segregation shows clearly, that, whatever may be the 

 nature of Mendelian segregation at the formation of germ-cells, 

 these seeds must have passed through the process. In other 

 words, true, fertilizable ovules must in this case have devel- 

 oped spontaneously into viable individuals, good seeds. As each 

 of these individuals must have come out of one gamete instead 

 of two, each of them must have been pure for all its genes, and 

 any group of plants grown from such an individual must be a 

 real "pure line." In such material further tests would be super- 

 fluous, and any spontaneous hereditable variation in a self-fer- 

 tilized series with this origin might without further investiga- 

 tion be termed a mutation. 



We found the climate of Buitenzorg, Java, deadly for our 

 squashes. All our seed was dead within fourteen months, and 

 the two series of young plants from self- fertilized seeds of par- 

 theriogenetic plants could only with very great care be protect- 

 ed long enough against fungi and insects to show the shape of 

 the young fruit, and of the leaves. Thanks to the care of Mr. 

 van Helten of the Botanical gardens, we could observe that in 

 the descendants of a parthenogenetic F2 plant from the cross 

 Tiirkenbund x Poire bicolore there was no variation in fruit- 

 shape and during our illness, Dr. Smith of the Botanical Mu- 

 seum grew a number of plants from self-fertilized seeds of one 

 parthenogenetic F2 plant Miracle x Vegetable-marrow for us, 

 and reported uniformity in fruit-shape and leaf-shape. 



To resume our chapter on mutation, we have to conclude 



