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On the Result of Crossing Round with Wrinkled Peas, with 
Especial Reference to ther Starch-grains. 
By A. D. DARBISHIRE, Royal College of Science, London. 
(Communicated by J. Bretland Farmer, F.R.S. Received June 20,—Read 
November 14, 1907.) 
One of the characters with which Mendel dealt in his hybridisation 
experiments with peas was, as is well known, the shape of the ripe seed. 
Weldon, in his criticism* of Mendel’s interpretation of his results, showed 
that round were not discontinuously distinct from wrinkled peas, but that 
intermediate shapes connecting these two extremes were not infrequently 
exhibited. The answer which was made to Weldon’s criticism was that the 
intermediate shapes were due to spurious pitting or dimpling of the seed, 
and did not represent an intermediate condition of the germ which gave rise 
to them. And this answer was shown to be correct by the work of Gregory, 
who found that the starch-grains of round and wrinkled peas were quite 
distinct, and that they afforded an infallible test by which the real character 
of a pea with doubtful shape could be determined. 
Our knowledge of this subject has not advanced beyond the stage reached 
by Gregory in 1903; that is to say, we know no more about the inheritance 
of wrinkledness and roundness than Mendel did, except that each of these 
two characters is associated with a particular kind of starch-grain. What 
is the nature of the starch-grain in the hydrid; and how the characters 
of the starch-grains segregate, if they do so at all, in subsequent generations, 
are points on which we are at present ignorant. The observations, which 
have to record, form the first instalment of an attempt to fill up this gap in 
our knowledge. 
Part of the cost of these experiments was defrayed by a Government 
Grant. 
The Starch-grains of the Round Pea. 
The grains in a round pea such as “ Eclipse ” are, as shown in fig. 1,} single, 
potato-shaped grains. They will be referred to for the sake of brevity as 
p-grains. Their average length is 0°0322 mm., their average breadth 
* ‘ Biometrika,’ vol. 1, p. 231. 
+ ‘The New Phytologist,’ vol. 2, No. 10, p. 226. 
{ Fig. 1 is magnified slightly less than figs. 2 and 3. The actual sizes of the types 
of grains figured is given in the text. All the grains described have been derived 
(as far as possible) from the deeper layers of the cotyledon as distinguished from the 
superficial ones where the grains are smaller. 
