Varietäten, Descendenz, Hybriden. 55 



In conclusion it is admitted that somatic inheritance is difficult, 

 and often lacking where expected ; yet it is the very root of evolution 

 on the mnemic hypothesis by which memory rules the plasmic link 

 between successive generations. F. F. Blackman. 



Mapryat, Dorothea C. E., Hybridization Experiments with 

 Mirabilis Jalapa. (Rep. Evol. Comm. Roy. Soc. London, V. p. 

 32-50. 1909.) 



The experiments deal with the inheritance of flower-colour. 

 Three colour varieties have been used, namely white, yellow and 

 crimson. Of the seven white plants used one has been found to differ 

 in composition from the remainder in that, when crossed with yellow, 

 it gave pale yellow (and not red) hybrids. This white therefore lacks 

 the factor, present in the other whites examined, which has the 

 effect of turning the yellow sap colour red. This white when crossed 

 with crimson gives in Fj the same series of coloured forms as was 

 obtained when the other whites were crossed with yellow, but un- 

 complicated by the flakin g which appears in a proportion of the 

 F2 in the latter case. 



The two kinds of white crossed together give coloured forms. 

 The F, of these crosses consisted of 12 plants with white flowers 

 flaked with magenta, and one plant with self-coloured magenta-rose 

 flowers. It may be assumed therefore that iwo factors are necessary 

 for the production of colour, of which one is present in each kind 

 of white. The flaking is brought in here, as in the other cases, by 

 one of the white parents. 



The heterozygous coloured forms are always distinguishable 

 from the pure types, and the interrelationships of the various coloured 

 types which appear in the Fj series are shown in a table, in which 

 the factorial composition of each colour is set out. 



The inheritance of the flaked character cannot as yet be fully 

 explained. In F^ where white-flaked as well as pure white occur, 

 the two combined always make up approximately the expected number 

 of pure whites of which there is otherwise an unaccountable shortage. 

 In cases where there was no complication by flaking the expected 

 number of pure whites was always very closely obtained ; but for 

 the cases where flakes appear no simple factorial scheme can as yet 

 be proposed which will represent consistently the three facts — 



(1) that F, from white X self-colour may be flaked with yellow pigment 



(2) that F2 from such a cross contains whites as 1 in 16 instead 

 of as 1 in 4, which is the ratio in which they appear when no flaked 

 forms occur; (3) that though the flaked forms occasionally throw 

 self-coloured individuals, this phenomenon is so irregulär that its 

 significance is quite uncertain. R. P. Gregory. 



Vogler, P., Variationsstatistische Untersuchungen an 

 den Blättern von Vinca minor L. Ein Beitrag zurTheorie 

 des Flächenwachstums der Blätter. (Jahrbuch der St. 

 Gallischen naturw. Ges. 1907 (1908) p. 1—31.) 



Das Gesetz von Quetelet sagt, dass die Variation eines Merk- 

 mals sich symmetrisch um ein Zentrum grösster Dichte gruppiert; 

 bildlich durch eine eingipfelige Kurve darzustellen. Bei Unter- 

 suchungen botanischer Objekte stimmt nicht immer die eingipfelige 

 Kurve, sondern es treten mehrere „Nebengipfel" auf. Diese Gipfel 



