222 MASS MUTATIONS AND TWIN HYBRIDS OF 



vated in large numbers of the second generation, which is uniform. 

 It is as high as ovata, but less stout; its branches are more erect, 

 its flowers and fruits erect and almost pressed against the stem. 

 The leaves are smooth and narrow, measuring approximately 

 1.5 x 8.5 cm. (as compared with 4x17 and 4.5 x 14 in the two 

 others) and the stem and foliage are brownish contrasting sharply 

 with the two other types. Even in early youth the differences are 

 sharp enough, although some individuals may remain doubtful, 

 especially when the space at their disposition is not sufficient, but 

 the flowering spikes make all doubts disappear. 



0. hybr. mut. contraria resembles the brunnea, but has larger 

 leaves, measuring approximately 2.5 x 10 cm, and the color is less 

 brown. The flower buds are thinner and yellowish. It looks like a 

 different combination of the marks of the triple hybrids. Perhaps 

 it is related to 0. Lamarckiaiia mut. oblonga. 



0. hybr. mut. gigas. — This occurred in the first generation of a 

 cross between 0. lorea and 0. Lamarckiana, and in another between 

 0. grandiflora and 0. nanella. Both were recognized by their broad 

 flower buds, resembling those of 0. Lamarckiana gigas. The first 

 was a stout plant 1.5 m. high, but little branched, with broad and 

 thick leaves, a short and thick calyx tube, and short and thick 

 fruits. In its other marks it belonged to the type ovata. Its pollen 

 consisted almost entirely of quadrangular grains, which were almost 

 completely fertile. Moreover, it was fertile after self-fertilization. 

 Its seeds contained 89 germs in 100 grains. Evidently it was a 

 gigas and not a semigigas. The other mutant was a lutea with thick 

 flower buds. It produced with its own pollen only one fertile seed, 

 which germinated in 1916. Unfortunately this seedling was attacked 

 by some disease, but it flowered in September with the buds, flowers,, 

 and pollen of a pure gigas, and showed 28 chromosomes in the 

 nuclei of its roots in preparations made for me by my assistant 

 Mr. C. van Overeem. 



0. hybr. mut. nanella were dwarfs like the hybrid dwarfs of 0. 

 Lamarckiana. They appeared in the second generation of lutea 

 specimens from crosses between 0. Lamarckiana x lorea and 0. 

 lorea x nanella. 



I made my crosses in different years and cultivated about 30 or 

 60 offspring of each. I counted them in July at the beginning of 

 the flowering period, when the characters were most sharp and no 

 doubtful specimens remained. I made one cross first in 1913, and 

 the others in the two following years, so as to have cultures of the 



