MENDELIAN CHARACTERS IN PLANTS AND ANIMALS. 121 
tallness on a dwarf basis, as in the peas, while long and round pollen 
might be regarded as presence and absence of longness on a round basis, 
presence being dominant in both cases. 
POPPIES. 
In my experiments with Papaver somniferum, three pairs of Mendelian 
characters were met with, viz. coloured and white flowers, purple and red~ 
flowers, black and white basal area of petals—the first-named of the pair 
being dominant over the other, which is recessive. The first two pairs 
are probably, like the sweet pea, due to three pairs of unit-characters— 
presence and absence of C, presence and absence of R, presence and 
absence of B—presence being dominant.. The remaining pair, black and 
white basal area of petals, may be regarded as presence and absence of 
black pigment, presence being dominant. 
ANTIRRHINUMS. 
In my experiments with Antirrhinum majus, as we have already seen, 
two pairs of Mendelian characters have been found, viz. white and 
yellow corolla segments, red and yellow corolla segments, the first of the 
pair being dominant over the other, which is recessive. The unit-characters 
in these two cases seem to be absence and presence of yellow sap, presence 
and absence of red sap, respectively, presence being recessive in the yellow, 
and dominant in the red, 
ToMATOS. 
In my experiments with tomatos, as already seen, two pairs of Mendelian 
characters have been found, viz. red and yellow flesh, yellow and white 
skin, the first-named of the pair being dominant over the other, which is 
recessive. The unit-characters in these two cases seem to be presence and 
absence of red in the flesh, and presence and absence of yellow in the skin, 
respectively, presence being dominant in both cases (see fig. 26). 
PRIMULAS, 
In my experiments with Primula, three pairs of Mendelian characters 
were met with, viz. red and green stems, palm and fern leaves, thrum and 
pin eyes, the first-named of the pair being dominant over the other, 
which is recessive. 
Red and green stems may be regarded as presence and absence of red 
on a green basis, presence being dominant and absence recessive. 
The application of the presence and absence hypothesis to palm and 
fern leaves is not so obvious. 
If we regard this as presence and absence of palm on a fern basis, we 
are at once met by the difficulty that the fern leaf appears to be an 
elongated palm leaf. If, on the other hand, we regard it as presence and 
absence of fern or a palm basis, this would imply dominance of fern over 
palm in the zygote, while experiments show, on the contrary, that palm 
leaf is dominant over fern leaf. Similarly with thrum and pin eye, if we 
regard it as presence and absence of thrum on a pin basis, we are met by 
the difficulty that pin eye or long style seems to be an elongated thrum or 
