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A. D. Dar bis hire. 
in the latter the cell is crammed with the starch-grains and there 
seems little room for anything else. And lastly the wrinkled 
Pea tastes distinctly sweeter than the round one, which in 
comparison has a very bitter taste. In connection with this last 
fact it is of no small interest to note that nearly all, if not actually 
all, of the improved Peas offered by Messrs. Sutton are wrinkled. 
What is the source of the sugar in the wrinkled Peas? It is pre¬ 
sumably the remains of the sugar, in which form the reserve material 
was laid down, which has not been converted into starch. We are 
thus immediately led to the hypothesis that the pair of factors to 
which the shapes of the cotyledons of Pisum are due, are, not 
“round” and “wrinkled,” but some factor which completes the con¬ 
version of sugar into starch and the absence of this factor. I say 
“completes the conversion ” and not “ effects the conversion” because 
some starch is formed in the wrinkled Pea: the difference between 
the two lies in the fact that some, but not all, of the sugar remains 
unconverted in the wrinkled Pea. 
It has long seemed to me that of all the characters in animals and 
plants, the Mendelian inheritance of which has been demonstrated, 
this is the one the investigation of which seems to offer the surest 
prospect of describing the two units of a pair of characters in 
chemical terms. And I am at present engaged in the investigation 
of this material along these lines. There cannot be any doubt 
that such knowledge would be of the greatest scientific, and possibly 
of practical value. If the latter were to prove true it would be a 
curious, but satisfactory paradox that the re-investigation of a case, 
which might at first sight appear to be of purely historical and 
academic interest (the shape of the cotyledons being the first on 
Mendel’s list of seven characters) should have such a result. 
To return, however, to the Presence and Absence hypothesis: 
I propose now to consider one or two instances in which its appli¬ 
cation seems to be attended with greater difficulty than has been 
the case with those which we have already considered. 
Under the heading, “Apparently parallel cases which are 
conflicting ” (with the emphasis on the “ Apparently ” and not on 
the “parallel”) let us consider the following paradox. Urtica 
pilulifera is the ordinary nettle with deeply serrated leaves. In U. 
Dodartii the bays are, so to speak, filled in ; and the margin of the 
leaf is entire. The pilulifera character is dominant to the Dodartii 
character; i.e., dissectedness is dominant to entirety. Chelidonium 
majus has a variety, var. laciniatum. But in this case the character 
