STOUT AND 8USA, CHROMOSOME IRREGULARITIES £1 



vulgaris, of Tischler (1906) for the hybrid Ribes Gordonianum (recent- 

 ly reinvestigated by Tischler, 1927) and of Rosenberg (1909) for 

 Drosera obovata. Hybrids are frequently more or less sterile from abor- 

 tion of spores and sex cells and this involves a rather wide range of 

 nuclear and chromosome irregularities not only when the two sets of 

 parental chromosomes are unequal in number but also when the num- 

 bers are equal. 



There seems to be rather general agreement that in the sterility of 

 hybridity the irregularities occur during meiosis, particularly in the 

 non-pairing of univalents and in their subsequent irregular distribution. 

 It is characteristic of the sterility of hybridity that the abortion de- 

 velops to the same degree in the formation of both the microspores and 

 the macrospores, which indicates that the abortion involves funda- 

 mentally incompatible relations between chromosomes. 



In a recent paper Blaringhem (1928) considers that the Europa Day- 

 lily arose as a hybrid. This view is based in part on the high degree 

 to which abortion of spores occurs and in part on the results of his 

 breeding experiments. In using pollen of Europa in crossing with 

 H. /Java he obtained plants of the first generation and also he grew a 

 second generation, but all were yellow-flowered, as is H. fava. There 

 was in their flowers no trace of the fulvous-red coloring characteristic 

 of H. fulva. In further use of the pollen of Europa on flowers of H. 

 flava and H. auranteaca, out of a considerable progeny only two had ful- 

 vous-red coloring in the flowers. Evidently these two plants were the 

 only ones that were hybrids. These differed in vigor of growth and in 

 sterility and because of this it was assumed by Blaringhem that the 

 Europa parent is itself a hybrid. 



In the breeding of day lilies at The Xew York Botanical Garden 

 plants of H. fava have been highly self-compatible and also frequently 

 self-pollinating before flowers open. But where flowers are emasculated 

 in the bud before pollen is shed, the properly guarded pollinations with 

 pollen of the Europa clon give in every case F 1 hybrids that possess 

 considerable fulvous red in the coloring of the flowers. This is likewise 

 the case for the reciprocal hybrids. In the next generation obtained by 

 crossing F x plants or of back-crossing with Europa there has been great 

 variation in vigor of growth and in the degree to which fulvous color- 

 ing is developed. This may mean that Europa is itself heterozygous 

 or that the inheritance of its fulvous coloring is on the basis of mul- 

 tiple factors. The species to which the Europa clon belongs is a vari- 

 able one, judged by the wild plants obtained from China and Japan. 



