3G4 
PEOFESSOR K. PEARSON AND OTHERS ON 
Appexdtx. 
On the Homotyposis of the Pods of Leguminous Plants. 
I have already indicated that I had initially grave doubts as to whether a true 
measurement of homotyposis could be obtained by counting the ripe seeds in the 
pods of leguminous plants; but that a passage in a work of Darwix’s led me to 
modify my opinion, and when finishing my memoir, I found time to incorporate in it 
the broom series from Danby Dale which seemed to confirm Daewix’s views. Broom 
is cross-fertilised and much visited by insects, and accordingly the statement made 
onp. 334 of this memoir appears to have full validity. As the matter seemed of some 
interest, I suggested to Miss C. D. Fawcett a fuller study of leguminous plants 
from this standpoint. Her results have reached me in time to be reduced by Dr. Lee 
and to be incorporated in this Appendix. I have myself worked series for the common 
bean and the tare vetch, so that if these be included we have now a fairly extensive 
range of material from which to draw conclusions. 
I will first give the data and state the manner in which it has been reduced, and 
then consider the results which flow from its consideration. The following is a list 
of the species dealt with ; I have remarked on some of the difficulties arising in 
the course of our work. 
(i.) Cytisus Scoparius. Broom from Danby Dale {see p. 334).—It was found difficult 
to count the total number of ovules, and only the ripened seeds were dealt with. 
The plant is cross-fertilised. The pods were fairly free from insects. 
(ii.) IjOtus Corniculatiis. Bird’s-foot trefoil from the neighbourhood of Lyme 
Begis, Dorsetshire.—The aborted seeds could not be counted, and the pods were 
largely frequented by grubs, so that it was occasionally doubtful how far ripe seeds 
had been destroyed. The number of pods on each plant in this first series were too 
few too allow those with grubs in them to be neglected.* 
(iii.) Lotus Corniculatiis. —A second series from the neighbourhood of Lyme Begis. 
This series consisted of more vigorous plants from a slightly different environment, so 
that fourteen to twenty pods could be gathered from each, and thus difficulties as to 
the possible destruction of ripe seeds by grubs avoided. It would appear that the 
effect of rejecting such ]3ods has raised the mean number of seeds, but at the same 
time artificially reduced the homotyposis. The plant is cross-fertilised. (Darwix : 
‘ Cross and Self-Fertilisation of Plants,’ p. 361.) 
(iv.) Lathyrus Odoratus. Sweet Pea.—This was obtained from a row in a nursery 
garden at Lyme Begis. Both the fertilised and aborted seeds were counted, so that 
the total number of ovules could be found. The plant is said to be cross-fertilised in 
* As an illustration of tliis sort of difficulty I may note that I found something like 90 per cent, of the 
pods of gorse in the Danby district so full of insect life that nothing could be done in regard to counting 
their seeds. 
