W. F. R. Weldon 
243 
a piebald white and blue seed, or a seed of uniform but intermediate colour. The 
peculiar process of double fertilisation to which this change of colour in the extra- 
embryonic tissues of Maize is due does not seem to me to affect the relevance of 
the observations. 
In order to emphasize the need that the ancestry of the parents, used in 
crossing, should be considered in discussing the results of a cross, it may be well to 
give one or two more examples of fundamental inconsistency between different 
competent observers. 
Correns (No. 5) himself has crossed the Stock Matthiola annua = M. incana 
D.C., which has its green parts covered with grey hairs, and the smooth-leaved 
Stock, il/. p'Za6?-a D.C The 111 hybrids obtained from reciprocal crosses all had 
hairy leaves. Trevor Clarke made a similar cross, using of course different 
races, and found that half his seedlings had smooth leaves, half had hairy leaves 
(No. 2).* Again, the petals of the M. incana used by Correns were violet, those 
of the M. glabra were yellowish white. The petals of the hybrid seedlings were 
invariably either violet of the shade of M. incana, or violet more or less obviously 
spotted with pale violet. On the other hand, Nobbe (No. 23) crossed a number 
of varieties of M. annua in which the flowers were white, violet, carmine-coloured, 
crimson, or dark blue. These were crossed in various ways, and befoi-e a cross 
was made the colour of each parent was matched by a mixture of dry powdered 
colours, which was preserved. In every case the hybrid flower was of an inter- 
mediate colour, which could be matched by mixing the powders which recorded 
the parental colours. The proportions in which the powders were mixed are not 
given in each case, but it is clear that the colours blended. 
Again, de Vries (Nos. 30 and 31) whose evidence for most of his statements 
concerning the validity of the law of dominance has not yet been published, crossed 
Datura tatula with the smooth^fruited form of D. stramonium. D. tatula has 
blue or violet flowers, and dull purple stems ; the flowers of D. stramonium are 
white and its stems bright green. De Vries found that in all his hybrid seedlings 
the flowers were blue, and he concludes that the colouring of D. tatula is 
dominant in Mendel's sense. Naudin (No. 22) crossed B. tatula with the variety 
of D. stramonium which has spiny fruit and wliite flowers. The flowers of his 
hybrids were violet, but paler than those of D. tatula, and their stems were 
flushed with purple, but to a less extent than those of I), tatula ; so that in his 
crosses a blending of the parental colours occurred. Again, de Vries found that 
the fruit of his hybi'ids was spiny, and concludes that the production of spines is a 
dominant character. Naudin crossed the smooth-fruited and the spiny-fruited 
forms of D. stramonium (which he called distinct "species") and found that among 
the fruits of forty hybrids some were completely spiny ; others were smaller than 
the normal fruits of the spiny form (in this resembling the smooth form), while their 
spines were shorter and weaker than in the pure spiny form ; others again were a 
* According to Bateson {Journ. Roy. Hort. Soc. Vol. xxiv. p. 64), Miss Saunders has obtained a 
similar result. Correns doubts whether Trevor Clarke's flowers were completely cross-fertilised. 
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