212 MASS MUTATIONS AND TWIN HYBRIDS OF 



spring of the laeta contained two mutants, an ochracea and a lorea; 

 that of the velutina one, a sulfurea, with the same pale yellow petals 

 as in 0. biennis mut. sulfurea. Besides these, each of the cultures 

 was uniform, resembling the parent in all respects. The differences 

 were apparent in the boxes in May, at the time of planting out. 



0. syrticola x 0. grandiflora. — 0. syrticola Bartlett is the 0. 

 muricata of my Gruppenweise Artbildung. I made two crosses in 

 1913, crossing each plant with the pollen of one individual of 0. 

 grandiflora, as usual. The figures for both cultures are given separately 

 in table III; one of them was grown in 1914, but the other in 1915. 

 From the first I had a second generation for each of the twins in 

 1915 and a third in 1916. They were uniform and resembled their 

 parents. The size of these cultures was 4 and 49 for the laeta, but 

 61 and 70 for the velutina, which had given a better harvest. One 

 mutant was observed among the velutina of 1915, having linear 

 leaves and remaining very weak; apart from this the cultures were 

 strikingly uniform, with the same differences as in the first genera- 

 tion and almost the same as those between the twins of syrti- 

 cola x Lamarckiana. 



In this first generation the differences were observed in the be- 

 ginning of June, since the velutina were small plants with narrow 

 kennel-shaped leaves, whereas the laeta were stout and had broad, 

 flat leaves. These differences increased in July and August during 

 the flowering period. The laeta were grass-green, but the velutina 

 more gray; these latter had broad flower buds (7 x 22 mm. as 

 compared with 5 x 27 mm. in the laeta). The petals were somewhat 

 larger (3 cm.) in the laeta and smaller (2 cm.) in the velutina. The 

 fruits were thin in the first named hybrid, but conical in the other. 



0. suaveolens x 0. grandiflora. — I made this cross in 1915 and 

 cultivated only the first generation. It consisted of 61 per cent 

 laeta, 21 per cent velutina, and 18 per cent of a third type, among 

 69 specimens, most of which have flowered. The three types were 

 discerned in June and evident in July and August, although the 

 differences between laeta and velutina were only small. Height of 

 laeta in July 60—80 cm., of velutina 40—60 cm., midveins reddish 

 in the first, white in the second. Leaves 3x10 cm. as compared with 

 3 x 15 cm. in July, and 3.5 x 11 cm. as compared with 2x9 cm. 

 in August. The flower buds and flowers showed only small diffe- 

 rences. The remaining 18 per cent were set off sharply against the 

 rest, and this from the very beginning. They had the pale color, 

 broad leaves, and low stature of the corresponding mutants of both 



