INBREEDING EXPERIMENTS 133 



apparent in details of plant and ear structure which are 

 difficult of statistical expression. The beautiful uni- 

 formity of these plants in all characteristics at the pres- 

 ent time is one of their most striking features. This can 

 be seen fairly well for the ear characters in accompany- 

 ing illustrations (Fig. 29). In the minutiae of the tassels, 

 leaves and stalks they show the same striking uniformity. 

 These minor details which characterize each of these 

 groups of plants are difficult to describe adequately, but 

 are perhaps the most noticeable feature about them. 

 The tassels or the ears of all these four Learning 

 strains, if mixed together, could be separated without 

 the slightest difficulty. 



Some characters appear so rarely in plants they have 

 been generally considered to be due to what might be 

 called physiological accidents rather than to inheritance. 

 An illustration of this kind is furnished in maize by the 

 occurrence of doubled or connate seeds. Instead of one 

 embryo enclosed in a pericarp, separate embryos and 

 endosperms are present, with the seeds arranged back 

 to back and the embryos facing in opposite directions. 

 A few seeds of this kind have been described from time 

 to time, but never more than one or two on an occasional 

 ear. From twelve inbred strains of a variety of maize 

 other than the ones previously described, two lines have 

 been obtained which produce these peculiar seeds as a 

 common feature. One of the strains shows from one to 

 six or more on practically every ear. The second strain 

 shows them more rarely and the other ten strains derived 

 from the same variety have never been observed to bear 

 them. Here, then, is a character which does not appear 

 except at rare intervals when the plants are crossed 



