46 



not know whether the Evening Primrose which he investi- 

 gated was a pure race or of hybrid origin. 



To horticulturists a knowledge of hybrids is of the 

 greatest importance, a vast number of new and interesting 

 forms being continually produced through hybridisation. 

 .\t one time it was thought that hybrids were invariably 

 intermediate between the two parental forms, and that they 

 were generally sterile, and could therefore not be repro- 

 duced by seed. Though this is sometimes the case,, 

 particularly where the parents are of different species, it is 

 by no means the rule, and certainly not in the case of 

 hybrids between two different varieties. Our exact know- 

 ledge of hybrids dates from the careful experiments made 

 in the latter half of the nineteenth century by Gregor 

 Mendel^ of Briinn. Unfortunately, his important investi- 

 gations did not becom^e generally known until die begin- 

 ning of the present century. ]\Ienders first observations 

 were made on various varieties of the garden pea, and he 

 obtained the striking result that in crossing two different 

 strains the offspring were not of immediate type, but 

 generally inherited the characters of one of the parents in 

 their entirety. Thus in crossing varieties, of which one 

 had round and smooth and the other wrinkled seeds, he 

 obtained seeds all of which were round. He therefore 

 considered this to be a dominant character, while he called 

 wrinkledness recessvve. But when the flowers of the hybrid 

 plant were subsequently fertilised with their own pollen, 

 the seeds they produced were not all round, some of themi 

 were wrinkled like those of one of the grand parents. On 

 carefully counting the number of these recessive types, he 

 found that one m four had reverted to the wrinkled tvoe. 

 Aloreover, he found that of the round seeds some were of 

 pure type, and when further cultivated always produced 

 round seeds, while others were of hybrid nature and these 

 always produced reversions to the parents which had been 

 originally crossed. 



He was able, finally, to demonstrate that of the off- 

 spring of every hybrid when self -fertilised one quarter 

 reverted completely to the female parent, one quarter to 

 the male parent, while half of the offspring remained of 

 hybrid nature. These resembled the parent, which pos- 

 sessed the dominant character but preserved the recessive 

 character in a dormant or latent form as was shown by its 

 reappearance in a subsequent generation. The accurate 



