New Yokk Agricultukal Expekiment Station. 827 



they transmit to their descendants, the character they do not show. 

 Others still, about half when the number of descendants is large, 

 are like the first generation, containing both unit characters, the 

 " recessive " hidden by the " dominant." These latter animals 

 or plants, showing the " dominant " unit character resemble the 

 pure dominants outwardly in respect to this particular character, 

 but some of their descendants will show the recessive character; 

 which descendants of pure dominants never show. There are, of 

 course, hundreds of such pairs, and many characters not con- 

 trasted or balanced by others (technically known as "unpaired 

 genes"), since there are innumerable features and characteristics 

 in each animal or plant each of which may be made up of one or 

 several unit characters. Accordingly, the separate descendants 

 in any generation may be quite unlike through varied groupings 

 of the numerous dominants and recessives, and very careful 

 study is necessary to disentangle the mystery of inheritance ; 

 but we know that the law given above holds true for each pair 

 of unit characters. 



If two unit characters that make up any feature or character- 

 istic of a plant or animal be not opposed, though different, both 

 may appear in the first generation ; so that, with regard to that 

 particular feature, the good or bad points of both male and 

 female parent may come together in the descendant. For ex- 

 ample, if a plant with many long joints be crossed with one whose 

 joints are thicker and heavier, the descendants of the first gener- 

 ation may inherit both the length and the thickness, thus making 

 larger, stockier plants than those of either parent. 



Similarly, certain different, but not opposed factors that go to 

 make up vigor, healthfulness, or productivity may be united 

 when different strains are crossed; and the descendants, accord- 

 ingly, give better yields than either parent. In the second genera- 

 tion, with the splitting up of unit characters that takes place, 

 only half the descendants will carry the united characters ; and 

 the yield will tend toward a mean between that of the parents and 

 the first generation. With each subsequent generation the pro- 

 portion of plants bearing these joined favoring factors will de- 

 crease and the beneficial influence of the crossing be soon lost. 



The figures secured in these tomato experiments support this 

 theory admirably ; though we are not able to say what influences 

 united to give the favorable result in the first place. The con- 

 stitutional " unit characters " that make up vigor, health and 

 productiveness have not yet been separated. 



