Morphologie etc. — Varietäten etc. — Physiologie. 211 



and shows that the apparent dichotomy in a nuraber of roots is 

 really the result of injury to the root-tip. M. N. Owen (Kew). 



Pellew, C. and F. M. Durham. The genetic behaviour of the 

 hybrid Primula Kewensis and its allies. (Journ. Genetics. V. 

 p. 159—182. 1916.) 



The authors describe experiments with P. floribunda, P. flori- 

 bunda var. isabellina, P. verticülata and P. Kewensis after giving 

 a füll history of the origin of P. Kewensis together with a detailed 

 description of this and the other varieties. 



The numerous selfings and crossings carried out yielded the 

 following results and conclusions. 



1. From the cross P. verticülata by P. floribunda, or the reci- 

 procal, plants resembling the female parent are generally obtained. 

 These maternal hybrids rarely show any evidence of segregation 

 when used for crossing and usually, on self-fertilization, breed true 

 to type. Their origin as the result of parthenogenesis cannot be 

 held to be disproved. 



2. Occasionally hybrids of the form known as P. Kewensis are 

 obtained. These are of two klnds: one, partially sterile, having a 

 somatic number of chromosomes of 18 (diploid race); the other, 

 fertile, having 36 somatic chromosomes (tetraploid race). 



3. The hybrids, of whichever kind, are obtained in very small 

 numbers and great difficulty is met with in germinating any seed 

 obtained. Uncertain germination is common , however, to these 

 plants. 



4. The fertile type of P. Kewensis generally breeds true to type 

 when seif fertilized, segregating only in certain factors such as 

 degree of mealiness and flower colour. When crossed with the 

 parent types it commonly produces maternal hybrids, but in rare 

 cases gives evidence of segregation. 



5. The genetic behaviour of two plants of P. Kewensis was 

 peculiar. The offspring of these plants approached P. floribunda. 

 One of them was found to have 18 somatic chromosomes and the 

 plant exhibited segregation, giving rise to new forms that repre- 

 sented recombinations of floribunda and verticülata characters. 

 These plants are also peculiar in that their seed germinates freely. 



6. Among the above new forms are many shades of yellow not 

 previously known in these plants. The factorial interrelations of 

 these new colours have not yet been sufficiently investigated. 



7. This diploid segregating Kewensis has been crossed with 

 Kewensis tetraploid. From this cross plants intermediate between 

 P. floribunda and P. Kewensis have arisen and also a few plants 

 resembling P. floribunda. W. Neilson Jones. 



Kuhn, E., Dunkelkeimer und Substrat. (Ber. Deutsche bot. 

 Ges. XXXIV. p. 369-386. 1916.) 



Katalytische Lichtwirkung und Hemmungsprinzip sind die Angel- 

 punkte der beiden Theorien (Lehmann und Ottenwälder, ander- 

 seits Gassner), die sich in der Auffassung des Einflusses des 

 Lichtes bei der Lichtkeimung gegenüber stehen. Wie ist aber die 

 Tatsache zu erklären, dass manche Samen die vorzugsweise nur im 

 Dunkeln keimen, durch das Licht in der Keimung stark behindert 

 werden? Die drei bestehenden Theorien wurden ausgesprochen von 



