8 July, 1908.] linproTemtut of Cereals by SeLcctioji and Crossing. 407 



erratic way in which characters appeared in the offspring was confusing 

 and the very plasticity of the organism induced by the breeder's art seemed 

 to be inexplicable. 



^Iendelism. 



It is only within comparatively recent times that the manner in which 

 characters are transmitted in hybrids has been properly understood so 

 that precise scientific methods can be applied to them. 



It is found that they follow in the main a simple rule which has been 

 experimentally proved over and over again, and the law to which they 

 conform was discovered by Mendel about 1865, and the principle is called 

 Mendelism after its discoverer. Mendel began his experiments in hvbridi- 

 zation with the common edible pea, because it fulfilled the conditions he 

 considered necessary. In the first place it possessed differentiating 

 characters or points, and in the second place it could easily be secured 

 against foreign pollen. As regards differentiating characters, he dealt 

 with the following seven pairs and traced their inheritance separately for 

 each pair : — ■ 



(i) Seeds — smooth or wrinkled. 



(2) Seed coats — deeply coloured (grey) or nearly colourless. 



(3) Cotyledons or seed-leaves — yellow or green. 



(4) Pods — green or yellow. 



(5) Pods — inflated and stiff or wrinkled and soft. 



(6) Flowers — scattered or in a terminal bunch. 



(7) Stems— tall (6-7 ft.) or dwarf (1^-2 ft. 



The crossing of the pea,-flower is simple as it is fertilized by its own 

 pollen and insects are not necessarily concerned in it, as in the case of wheat. 

 In a young flower before the anthers containing the pollen have burst, the}' 

 are removed with their stalks by a fine pair of forceps and the flower is 

 enclosed in a Manila paper or muslin bag until a dav or two later. Then 

 the top of the pistil is dusted with pollen from the flower of the so-called 

 male parent and it is closed up again in its bag until it has set seedT The 

 pollen produces the sire and the ovule produces the dam, so that the pollen- 

 bearer is not strictly the male, nor is the ovule-bearer the female parent 

 but they are often erroneously spoken of as such. Mendel cross-fertilized 

 his peas once, and then noted the result for each pair of characters during 

 several generations and the results were remarkable. Cros.ses, for instance, 

 were made between tall and dwarf varieties which had been proved to breed 

 true to these characters and the result was in every case the same, no 

 matter which was the pollen-producing and which the seed-bearing parent. 

 It is often asserted that the hybrid resembles the pollen-bearing parent 

 more closely as regards its flowers, but shows greater affinity to the seed- 

 bearing parent in its foliage. Careful experiments, however, prove that the 

 results are the same when reciprocal crosses are made. Tall plants resulted 

 in every case and as they were evidently the dominant partner, he called 

 them dominants, while those of the dwarf habit receded from sight for 

 one generation at least and he called them reccssives. The seeds were all 

 gathered and sown next season, the flowers being allowed to fertilize 

 themselves and both tall and dwarf plants appeared but there were none 

 half-and-half. The tall plants were about three times as numerous as 

 the dwarfs and this proportion of three to one was found to hold good 

 in several experiments. Next season all the seeds were sown as before 

 and from the seeds of the dwarfs only dwarfs grew, while the seeds of 

 the tall were not all of the same nature. The seed of some of them pro- 

 duced tall plants only and the seed of others produced b'oth tails and 



