370 
PROFESSOE K. PEARSON AND OTHERS ON 
fertilisation on liomotyposis deserve still fuller and more direct investigation."^ I 
feel we know little as to the influence of external causes even on the completeness or 
incompleteness of self-fertilisation. So far as homoty230sis in the ^^ods of leguminous 
l^lants is concerned, I would draw conclusions based solely on averages, and state 
tliat ;— 
(i.) The liomotyposis in the case of either rijie or aborted seeds in the jiods oi 
plants seems weakened to one-half the average value it has in the case of characters 
not depending on fertilisation. Thus Darwin’s view, that differences in the number 
of ripe seeds depend ipion the constitution of the ^ilants, seems to be only jiartially 
true. Extraneous causes about which we are not very clear appear to be generally 
influential. 
(ii.) The extraneous causes which act in a random manner on the homotyjiic 
correlation seem to affect both self-fertilised and cross-fertilised jilants, and this both 
with regard to ripe and to aborted seeds. 
(iii.) The order of intensity of homotyjiic correlation is ovules, riiiened seeds, and 
aliorted seeds. 
The reduction of homotyiiic coi-relation in the case of the fertility of jiods may be 
profitably comjiared with the like reduction which we find in the case of the 
coefficients of inheritance of fertility and fecundity in man and the horse, t 
Other jioints worth noting, I think, in our results are those of Table LIT., which 
gives the correlation between ovules and ripe and aborted seeds. As we might 
anticijiate, the more rijie the fewer aliorted seeds, and vice versd. The correlation is 
negative, high for the everlasting jiea, remarkably low for the tare vetch. It is 
interesting to see tliat the correlation between the ovules and either rijie or aborted 
seeds is not very high. A large number of ovules not necessarily connoting either 
a very large number of ri^ie or of aborted seeds. In fact, in the case of the ever¬ 
lasting jiea, the numher of ovules has very small influence indeed on the number 
of seeds which rijieii. In tlie tare vetch only is the relationship more marked. 
Professor F. 0. Oliver tells me that in certain cases evolution ajipears to be tending 
in the direction of the jiod containing one ri^ie seed onljL It seems, therefore, that 
such relations as are indicated in Table LIT (and others of a like kind, for further 
observations ought certainly to he made) may l)e useful in indicating the degree of 
fixity between tlie number of ovules and the nnmlier of rijie or aborted seed which 
are ultimately to lie found in the seed vessel. 
While the ovnles have the least and the aborted seeds the greatest variability, as 
measured liy the coefficient of variation, the ovules have the most and the aborted 
seeds the least homotypic correlation. Tliis might at first sight ajipear to he opposed 
to the view expressed on j). 363, that there is no relationshiji between the intensities 
* It seems to me that investigations of this kind ought to he carried ont by those who have, what I 
nnfortnnately liave not, the needful land for experimental investigations. 
t ‘Phil. Trans.,’ A, vol. 192, p. 277 ct seq. 
