i9i 2l CURRENT LITERATURE 351 



of the crown gall, and believes that "we have in the crown gall a striking 

 analogy to what occurs in malignant animal tumors/' He does not claim that 

 the animal cancer and crown gall are due to the same organism. The latter 

 part of the paper is devoted to physiological characters of the organisms and 

 presents some suggestions which will be of importance to the plant physi- 

 ologist who has the courage to attempt to explain the formation of plant 

 cecidia as a result of irritation by parasitic fungi and insects. — Mel T. Cook. 



Inheritance in flax. — Tammes 34 has studied a number of characters 

 m crosses between two varieties of the common flax {Linum usitatissimutn) 

 and between these and L. crepitans and L. angustifolium. She has dealt 

 quantitatively with the length of seeds, length and breadth of petals, color 

 of the flowers, degree of opening of the mature capsules, and the hairiness 

 of the dissepiments of the capsules. Hairiness of the capsules and the lightest 

 blue color of the flowers are each determined by a single Mendelian gene, but 

 all the other characters are obviously more complex. The author believes 

 that all of these characters are likewise determined by genes which segregate 

 normally in the F 2 , though they cannot be followed individually because 

 several genes affect the same characteristic and act together in such a way that 

 the grade of development of the character depends approximately on the 

 number of these genes present. This results in a continuous series of grada- 

 tions which are superficially indistinguishable from fluctuations, but which 

 differ by being inheritable. Several evidences for the correctness of this 

 interpretation are reported: The Ft is in each case intermediate between the 

 parents and no more variable than they; in the F 2 the variability is considerably 

 increased, and the curves stretch out toward those of either parent, but fre- 

 quently fail to reach them owing to the small size of the families investigated ; 

 when F 3 families are grown from the extreme variants of the F 2 , a still closer 

 approach to one or the other P x results, apparent identity with the parental 

 type being attained in several cases. From the proportion of F 2 and F 3 

 families which approached in any given characteristic the condition of the 

 Pi generation, Miss Tammes estimates the number of genes probably involved 

 m differentiating the two parental types in each cross with respect to the 

 several characteristics studied. She concludes that in length of seeds not less 

 than four differentiating genes were involved in every cross made, in some 

 crosses certainly a still larger number. In width of petals the simplest cross 

 must have had differences between the parents in 3 or 4 genes, and the other 

 crosses a considerably higher number. In flower-color different intensities 

 of blue were apparently dependent on three genes. Between capsules which 

 remain closed at maturity and those that spring wide open, 3 or 4 genes are 

 involved. Later generations will be needed fully to test these conclusions. 

 °eo. H. Shull. j 



34 Tammes, T., Das Verhalten fluktuierend variierender Merkmale bei der Bas- 

 tardierung. Recueil Trav. Bot. Neerlandais 8:201-288. ph. 3-5. 1911. 



