Mechanisms of Chromosome Congression during Mitosis
IN a preliminary aecmmt of the genetics and cytology of Dahlia (Lawrence, 1929) it was shown that, with the exception of D. va,riabilis, Dahlia species could be divided into two distinct groups for flower colour: Group I (ivory-magenta) ~ and Group II (yellow-orange-scarlet). Both series occur within D. vaHabilis. Flower colour in this species is the expression of two series of soluble pigments: (a) the flavones, (b) the anthocyanins. The flavones constitnte the "grolmd" colom's upon which the anthocyanins are snperposed. The grmmd colours range from ivory to deep yellow. The anthocyanin colom's appear as magenta to pm'ple, or orange to scarlet, according to the intensity of pigmentation and the colom" of the ground upon which they are sn]?erposed. Ivory florets can be recognised fl'om white by fuming them with ammonia. White gives no reaction; ivory tm'ns a g o o d lemon co]ore'; yellow changes to an intense orange. All ivories and whites in these experiments have been tested by fuming.