1911] The Ottawa Naturalist. 35 



cent observations and conclusions of recognized authorities show, 

 however, that this process takes place more often than is common- 

 ly supposed, although it is by no means frequent. 



When one remembers Mendel's own annunciation, however, 

 that it is only necessary to cross two individuals which differ in 

 ten different characters in order to produce over 1,000 distinctly 

 different hereditary forms, it will readily be seen how great may 

 be the confusion (variation) which must follow within a popu- 

 lation through the natural segregation of the heterogenous 

 progeny in successive generations. This dividing up of the 

 progeny of a crossing is now generally regarded as the variation 

 which Darwin described but was unable to explain. 



The speaker showed a large number of samples of oats from 

 Pure Lines taken out of the old Probestier variety, the common 

 white oats grown in the Baltic region. These samples were ar- 

 ranged to show the gradations in characters from one extreme 

 to the other. Thus there was shown a gradation in awniness 

 from an absolutely awnless sort to one which was heavily awned, 

 the gradation between the two conditions being a very gradual 

 one. Other lines out of the same variety were arranged to show 

 the same gradations in size, shape and color of kernel. 



A very large number of these pure lines from this variety 

 have been worked with in Sweden and Denmark, the best sorts 

 now in use in these countries having originated in this way. So 

 great had been the multiplicity of distinct hereditary forms in 

 this old variety that the experts in charge of the breeding oper- 

 ations found it difficult to obtain identical progeny from any two 

 individuals. These different forms were not regarded as muta- 

 tions but as the product of natural crossing. The experience 

 in artificial crossing work had led Ehle, of Sweden, to state his 

 conviction that a single crossing between two sorts possessing 

 certain characters was quite sufficient to account for practi- 

 cally all the different forms now found in the above old variety. 



Strange forms. While the above forms can, without any 

 stretch of the imagination, be regarded as being traceable to a 

 common origin, other forms, more foreign in appearance, occur 

 from time to time which seem more difficult to account for. 

 Thus there may arise bearded heads of wheat in a bald sort, 

 white kernelled individuals may appear in a black oat sort and 

 vice versa, or they may appear in a red kernelled sort ; side oats 

 may appear in varieties which have branching panicles, etc. 



The above aberrant forms have been called atavists by 

 some, being regarded as the sudden reappearance of the character 

 of an ancestor; others have applied the name mutation. Ex- 

 perience has shown, however, that the majority of these forms 

 which appear in nature without any apparent preparation may 



