10 .SIZE INHERITANCE IN RABBITS. 



Kccht clarf man wohl jetzt mit diesem Fall vor den Augcn auch z. B. die 

 Differenzen an Ahrentypus beim Weizen und die darauf beziiglichen Spaltun- 

 gen, ebenso wie die Spaltungen von Grosseneigenschaften usw. unter denselben 

 Gesichtspunkt bringen. Die Theorie von der Gemeingiiltigkeit des genannten 

 Prinzips und von der Bedeutung desselben zur Erklarung der von Mendel 

 zuerst festgestellten und von den spateren Forschungen noch durchaus uner- 

 schiitterten Gesetzmassigkeit, die sich in der Erzeugung der verschiedenen 

 Gameten jedes Merkmalspaares in gleicher Anzahl aiissert, diirfte durch solche 

 Falle, nur noch fester begriindet werden." 



The spikelets in a head of oats may be arranged on all sides of the 

 rachis, "Rispentypus," or all may be on one side, "Fahnentypus." 

 Nilsson-Ehle (1909) has found (from crosses between varieties having 

 these types of heads) that the Rispentype in five of eight crosses seemed 

 to depend on one factor. The first generation gave an intermediate 

 condition and three classes were found in the second generation in the 

 ratio, 1:2:1. In some crosses the ratios showed that more than one 

 factor was present determining the Rispentype. The Fahnentype 

 appeared in the absence of factors producing Rispentype. Baur (1911, 

 pp. 113-114) gives photographs of Nilsson-Ehle's plants, showing the 

 various types of heads. Preliminary studies on the beard of wheat and 

 waxy coating have been reported by Nilsson-Ehle (1908). He believes 

 that both of these characters may be produced by two independent 



T 1 f* t O T^ 



PHYSIOLOGICAL CHARACTERS. 



Several physiological characters have been investigated by Nilsson- 

 Ehle. These include winter hardiness, rust resistance, and time of 

 flowering. Whereas there is little doubt as to the occurrence of in- 

 creased variability in crosses differing in these characters, they have 

 not been completely investigated. In lines of Linum, some seed cap- 

 sules open when ripe, others remain closed. Tammes (1911) has made 

 crosses between such lines and found that FI shows capsules half opened 

 and that in F 2 there occurs a continuous series from the closed to the 

 fully opened type. 



Studies on the time of blooming of peas have been carried on by 

 Tschermak (1911). Early blooming varieties crossed with late bloom- 

 ing varieties produce offspring with intermediate blooming times. The 

 second hybrid generation shows great variability in the blooming 

 periods; some plants were earlier than the early parent, others later 

 than the late parent. The extremes inbred gave no intermediates, 

 but remained true for early or late blooming, or were even more extreme 

 than their F 2 parents. The intermediates in F 2 gave various results 

 in the following generation. Some seemed to show segregation into 

 two groups, others into three groups. So much is clear. Numerical 

 ratios between three groups (early, middle, and late) were calculated. 

 Those F 2 individuals falling within the ranges of the parental races 

 grown in the corresponding years were called respectively early and 



