KNOWLEDGE OF THE MUTATING- OENOTHEEAS. 31 



which I described several years ago (Gates, 1910 <?), hut were quite unlike them in 

 other features. This is another case of a mutation which is unable to perpetuate 

 itself, and its chief interest lies in showing how various are the germinal departures 

 from the parent form which may take place. 



The data regarding my cultures of O. ruhrinervis and O. 7m'bricaliix may now be 

 summarized. In 1907 I grew a total of 1112 plants of 0. ruhrinervis, all but 82 of 

 Avhich were the purely fertilized offspring of a culture of O. ruhrinet^vis plants, num- 

 bering 45, grown in the previous year, 15 of the latter being used as parents for the 

 second generation. The O. rubricali/x mutant appeared in this lot. One 0. rubrinervis 



mutant also appeared in 1907, in a culture of 170 plants of O. Lamarckiana from 

 pedigree seed. 



I shall not add anything to what is already published regarding O. ruhrlcalyx 

 (Gates, 1911 5), except to state that in 1911 I obtained a pure (homozygous) race, in 

 which all the rosettes exhibited the red character on their ventral surfaces. Six other 

 cultures of O. ruhricalyx in the Pg gave altogether 41 0. ruhncalyx and 51 0. rubri- 

 nervis. 



Regarding the nature of the change which led to the appearance of the 0. rubricalyx 

 mutant, it seems clear that the original mutant individual was heterozygous, and 

 originated from a cross between a germ-cell in which the new dominant character appeared 

 and one in which it was lacking. This is shown (1) by the fact that all the ruhricalyx 

 plants of tlie F^ tested were heterozygous, and (2) that the Pj from this plant con- 

 tained in addition to the 11 0. ruhricalyx, one O. ruhrinervis. The latter must have 

 originated from two germ-cells of the original mutant, both of which contained only 

 the recessive O. rubrinervis character. 



* 



The germinal change in the germ-cell which united with a normal 0. ruhrinercls 

 germ-cell to form this heterozygous mutant was, as I pointed out elsewhere (Gates, 

 1910 b), probably fundamentally quantitative — a difference in capacity for anthocyanin- 

 production which manifests itself throughout the plant. 



O. gigas. 



As is now well-known, this mutant has 28 chromosomes, double the number present in 

 O. Lamarckiana and most of the mutants. The structural changes which were corre- 

 lated with this nuclear change have been investigated in previous papers (Gates, 1909 d, 

 1911 c) and need not be further considered here, except to recall that the tetraploid 

 number of chromosomes is associated with a doubling in the volume of the nuclei and 

 a very large increase — in varying proportions according to the tissue — in the size of the 

 cells. It seems that the gigantic stature of O. gigas (which expresses itself in stoutness 

 of parts rather than tallness) results directly from the larger size of its cells, and it is 

 probable that the number of cells is approximately the same as in O, Lamarckiana, 

 Several similar cases which confirm this result have since been discovered in other 

 plants. Compare Wik&troemia (Strasburger, 1910), Mnsa (Tischler, 1910), Mosses 

 (E. & E. Marchal, 1909 and 1911). In animals, however, at least in Echinoderm and 



