EXPEEIMENTS IN PLANT HYBRIDISATION. 



11 



constant in this character ; 372, however, gave both round and angular 

 seeds, in the proportion of 3 to 1. The number of the hybrids, therefore, 

 as compared with the constants is 1*93 to 1. 



Trial 2. — Of 519 plants which were raised from seeds whose albumen 

 was of yellow colour in the first generation, 166 yielded exclusively yellow, 

 while 353, however, yielded yellow and green seeds in the proportion of 

 3 to 1. There resulted, therefore, a splitting into hybrid and constant 

 forms in the proportion of 2*13 to 1. 



For each separate trial in the following experiments 100 plants were 

 selected which displayed the dominant character in the first generation, 

 and in order to ascertain the significance of this, ten seeds of each were 

 cultivated. 



Trial 3. — The offspring of 36 plants yielded exclusively grey-brown 

 seed-coats, while 64 plants yielded partly grey-brown and partly white. 



Trial 4. — The oft'spring of 29 plants had only simply inflated pods ; 

 of the offspring of 71, on the other hand, some had inflated and some 

 constricted. 



Trial 5. — The offspring of 40 plants had only green pods ; of the off- 

 spring of 60 plants some had green, some yellow ones. 



Trial 6. — The offspring of 33 plants had only axial flowers ; of tlie 

 offspring of 67, on the other hand, some had axial and some terminal 

 flowers. 



Trial 7. — The offspring of 28 plants inherited the long axis, and those 

 of 72 plants some the long and some the short axis. 



In each of these trials a certain number of the plants came con- 

 stant with the dominant character. For the determination of the pro- 

 portion in which the separation of the forms with the constantly 

 persistent character results, the two first trials are of especial import- 

 ance, since in these a larger number of plants can be compared. The 

 ratios 1*93 to 1 and 2*13 to 1 gave together almost exactly the average 

 ratio of 2 to 1. The sixth trial has a quite concordant result ; in the 

 others the ratio varies more or less, as was only to be expected in view" of 

 the smaller number of 100 trial plants. Trial 5, which shows the greatest 

 departure, was repeated, and then in lieu of the ratio of 60 and 40 that of 

 65 and 35 resulted. The average ratio of 2 to 1 appears, therefore, as 

 fixed ivith certainty. It is therefore demonstrated that, of those forms 

 which possess the dominant character in the first generation, in two- 

 thirds the hybrid character is embodied, while one-third remains constant 

 with the dominant character. 



The ratio of 3 to 1, in accordance with w^hich the distribution of the 

 dominant and recessive characters results in the first generation, resolves 

 itself therefore in all trials into the ratio of 2 : 1 : 1 if the dominant 

 character be differentiated according to its significance as a hybrid cha- 

 racter or a parental one. Since the members of the first generation 

 spring directly from the seed of the hybrids, it is now clear that the 

 hybrids form seeds having one or other of the two differentiating cha- 

 racters, and of these one-half develop again the hybrid form, while the 

 other half yield plants tvhich remain constant and receive the dominant 

 and recessive characters in equal numbers. 



