HOMOTYPOSIS IN THE VEGETABLE KINGDOM. 
trees from Monmouthshire, Buckinghamshire, and Dorsetshire, gave results in good 
agreement; but sweet peas from two diftbrent nursery gardens in the same district 
give strikingly divergent homotypic correlations ! 
According to Darwin (‘ The Effects of Cross and Self-Fertilisation,’ 3rd edition, 
p. 153) the sweet pea “in this country seems invariably to fertilise itself” He bases 
this statement on (a) the difficulty of access to bees and other insects, (5) the fact that 
the varieties are habitually grown by seed growers close together, and yet the colours 
do not blend, (c) the experience that when the varieties are artificially crossed the 
colours do change. Professor Delphino, of Florence, in a letter to Darwin, writes 
that it is the fixed opinion of the Italian gardeners that the varieties do cross ; but 
in Italy other insects may of course be available. Now it is most remarkable that in 
Series I., whether the sweet pea be crossed or self-fertilised, the number of ripe seeds 
should be hardly individual at all. It would indicate that, with the particular 
environment of this series, the chance even ot self-fertilisation depends upon 
extraneous causes. The comparatively high individuality in the tendency to abort 
may mark some peculiarity of this variety; there may l)e a distinct inheritance of 
sterile tendencies to he kept sejiarate from an inheritance of fertility. But it is 
probably idle to guess at explanations of such discrepancies. I have gone carefully 
into the differences of environment in the two series which are interesting, although 
they do not obviously provide any key to the mystery. The first series were thickly 
planted in a long row, and the seed pods were gathered unripe. It was more 
difficult to separate each plant and to be cpfite certain that some of the seeds woidd 
not have had to 1ie reckoned as aborted in tlie fully ripened pods. The second series 
consisted of withered plants, the pods being almost all completely ripe; the peas 
were planted in separate groiqis a few feet apart. There was no difficulty in 
ascertaining the individuality of the plant nor as to the num])er of ripe or aborted 
seeds. About forty hives of bees were kept in the immediate neighbourhood of this 
second series the first series were at the other end of Lyme Begis, and removed 
from hives. Both series had had their flowers freely cut. I might have been 
prepared to attribute the low value of the honiotyposis in the sweet pea to this 
latter cause, but then the common liean and the tare vetch had not been subjected 
to any similar process, and they give on the whole mucli lower values. The ovules 
in either self-fertilised or cross-fertilised plants ought indeed to give a fair measure 
of homotyposis, but, for reasons already stated, it is not certain that our jirocedure 
in counting the perfect and the aborted seeds in the ripened pods has led to a just 
estimate of them. I am inclined on the whole to attempt no explanations for the 
anomalies observed in these seed investigations. The influences of self- and cross- 
* I mention this, as I noticed in Yorkshire fairly frequent but apparently ineffectual visits of the hive 
bees to sweet peas. It is possible that their attempts may assist the self-fertilisation, just as shaking or 
wind has been observed to do in other species. 
VOL. CXCVII.—A. 
3 B 
