480 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



colour-intensity, it is not reasonable to suppose that it has diminished 

 that of Shirley Poppies. 



One would like to be able to formulate some theory as to the total 

 disappearance of the one pigment, and the progressive disappearance of the 

 other, in this as in plants generally. 



Darwin's hypothesis of Pangenesis assumes that each particular 

 hereditary quality is determined by the presence of a special transmitting 

 body, or material-bearer of this quality, in the germ-plasm of one or both 

 of the parents. The hypothesis seems to be peculiarly applicable to the 

 inheritance of pigment, which is itself a material. Adopting this hypo- 

 thesis — and it seems the only possible one in the present state of our 

 knowledge — it may be applied to the sudden disappearance of the central 

 colour in Shirley Poppies, and to other albinos, in this way. 



Absence of colour means absence of pigment, and absence of pigment 

 signifies absence of the material substance in the plant which by inter- 

 action with other substances produces the pigment. This is the substance 

 which Eeinke has called chromogen (' Zeitschrift fiir Physik und Chemie,' 

 t. vi., 1883). From the earliest moment of the plant's life there must 

 have been, therefore, an absence of a certain material which is the generator 

 of this pigment. So that it seems reasonable to assume that the germ- 

 plasms of its parents, which by conjugation bred the little plant, wanted 

 the material-bearer of this quality — the determinant for the central 

 pigment of the flower. 



Assuming that the first plant which bore white-centred flowers was 

 developed from an egg and a pollen-cell which had no determinants for 

 the black central pigment, the two parents must have come together 

 fortuitously. If this was the first time such determinants had failed, the 

 chances that these two should come together are incalculable, and it is 

 therefore more reasonable to suppose that previous egg and pollen cells 

 had failed in this determinant, but that two such had not previously, so 

 far as is known, come into conjugation. 



Mr. Wilks informs me that he does not know of any instance of a 

 Shirley Poppy having been crossed with the typical form, but that he is 

 convinced that is the reason for the occasional production of black-centred 

 flowers from the trade-sold seed of Shirleys. It is extremely desirable 

 that this crossing should be done, and the progeny tested for the operation 

 of Mendel's Law, for the character is apparently never transmitted 

 reduced by one half, in Macfarlane's words, and it is therefore a clearly-cut 

 differentiating character about which no one could make a mistake. I 

 expect that Mendel's Law will be found to apply to this. 



The gradual disappearance of the other pigment shows that the colour- 

 determining substance for that is progressively diminishing, and that 

 therefore a determinant, at any rate for colour, may be present in the 

 LMTiii-pliisin to a greater or less extent. Because every generation shows 

 less of this pigment in the flowers, every generation must have less of this 

 particular colour determinant in the nuclei of the egg and pollen cells. 



Very late in the past season, too late to do much with them, and in 

 the course of examining the colouring-matter of flowers generally, I 

 selected some flowers from a large bed of Shirley Poppies, and gave them 

 a short examination. The seed had been obtained commercially, and 



