m 



KNOWLEDGE OE THE MUTATING OENOTHEEAS. 53 



noted. The numbers of plants are, unfortunately, often small on account of sterility, 



the biennial babit, etc. 



In regard to all these crosses, it must be said that fluctuating variability frequently 

 obscures'' the results and renders the formation of sharp categories very difficult. The 

 characters of these hybrids, such as broad and narrow leaves, are particularly responsive 

 to slight differences in nutrition, such differences producing in some cases great variation 

 the width of leaves in one type, in other cases obscuring tlie line between two 

 different types. Apparently the best conditions for displaying the laeta and velutina 

 characters are, in a rather poor soil, with very little fertilizer but plenty of water.. The 

 types then appear very sharply distinct, not only in width of leaf, but in colour, 

 pubescence, and crinkling. Owing to this obscuring fluctuation and to environmental 

 influences, I am still uncertain whether O. LmmrcUana X 0. hiennis and O. nanella X 

 O. hiennis yield a single fluctuating type or two types whicb are distinguished only 

 by width of leaf. The two crosses with O. ruhricalyx given in the table are merely 

 additional to those already published (Gates, 1911 &), in which it was shown that 

 0. ruhricalyx behaved the same as its parent O. riihrinerms. 



The two sharply distinct rosette types derived from 0. hiennis X O. Lamarchiana are 

 shown in PI. 5. fi"-s. 69 & 70, which represent laeta and velutina respectively. That 



O 



0. hiennis X 0. laevifolia yield two types wbicb are, in some crosses, identical with the 

 preceding, is shown by PL 6. figs. 11 & 72. The rosettes from this cross sometimes show 

 much variability, however, and I have obtained rosettes which were exactly intermediate 

 betweeii 0. hiennis and 0. laevifolia, as shown in PL 6. fig. 73 (cf. PL 4. fig. 50 and PL 2. 

 fig. 17). The basal jagged teeth of this hybrid are such as frequently occur in 

 a hiennis. Flowering shoots of the narrow- and broad-leaved hybrids derived from 

 O hiennis X 0. Lamarchiana are shown in PL 6. figs. 74 & 75, wbcre the difference in 

 width of stem-leaves is clearly seen. Other differences between these types, as regards 

 flowers, etc., have been described by Andrews (1910). 



As tbe twin types mature, their characters gradually converge, so that in the fruitmg 

 stage they are wholly indistinguishable. This is dne to the rapid diminution in length and 

 width of the bracts of both types. In PL 6. fig. 76 are shown, two-thirds natural size, 

 several buds of the velutina type from O. hiennis X O. Lamar cJciana , in which the bracts 

 pass from relatively broad and as long as the flower-bud, to very narrow and less than half 

 the len-th of the bud. The characteristic hairiness of this type of bud is also seen m the 

 photoo-raph [cf. PL 3. fig. 41 for 0. nanella and PL 4. fig. 53 for 0. hiemds). A fruiting 

 shoot of O. hiennis X 0. laevifolia is shown in PL 6. fig. 77. The twin types are at this 

 time whollv indistinguishable from each other and from the two types m 0. h 

 0. Lamai 



The measurements of tbe buds in 0. hiennis X O. laedfolia 



follows : ovary 11 mm., hypanthium 28 mm., bud-cone 20 mm., sepal tips 9 mm., 



petals 30 mm. maximum, usually less. 



The results derived from the reciprocal crosses are not quite so clear on account of the 

 obscuring effect of fluctuation, but in a general way there appears to be one rather widely 

 fluctuating type. Its broader-leaved varieties (which are the most frequent) are very 



