‘SELF-FERTILIZATION OF PLANTS. 319 
Intercrossed. Self-fertilized. 
Ipomea purpurea—ratio of heights . . . . . 100 106 
ia e So WEIS. ^ «o5. d^ bora 400 124 
Mimulus luteus - ,; leighis oce ad mes bas OO 101 
` SE ‘j Horoa tsoias et od: andy 100 103 
Digitalis purpurea — ,, BEEN | —. . —. IU0 94. 
» »* Wi og weight: 1.105.751 100 78 
A slight benefit was gained by the intercrossed "m of Eschscholtzia californica, 
Corydalis cava, and Oncidium (sp.). No benefit followed from intercrossing flowers on 
Origanum vulgare, Pelargonium (sp.), Reseda odorata, and Abutilon Darwinit. 
From these cases it appears that no benefit resulted in four cases, and with all the 
rest, excepting the weight of Ipomea, the advantage is so slight as to be comparatively 
insignificant; for the instances are too few,to be trustworthy for deducing broad or 
general results. It is, however, worth while observing, that the flowers of these species 
of Eschscholizia, Corydalis, Oncidium, and Digitalis are more or less usually self-sterile, 
the first three physiologically, the last morphologically so. That individual buds on a 
plant may be more or less, but probably rarely very greatly differentiated, is a fact well 
admitted, and treated by Mr. Darwin elsewhere under the title of bud-variation: and 
when such flowers are crossed, some benefit is likely to accrue to the resulting seeds ; for 
when flowers are more or less self-sterile, it shows that their sexual organs have become 
more highly differentiated than usual. Hence one would, à priori, expect that more 
benefit would result from their crossing than with flowers which had been less differen- 
tiated, as is doubtless the case with most flowers on one and the same plant; so that we 
have a reasonable explanation from crossing different flowers on the same plant of Esch- 
scholtzia californica, Corydalis cava, Oncidium (sp.) *. 
The fourth kind of union is self-fertilization; and although Mr. Darwin seems on 
several occasions to be strongly inclined to recognize some benefits as resulting from this 
process, as in the passages to be quoted presently, yet he repeatedly insists upon, not 
merely what I should prefer to call the negative results, but the “ evil effects” of self- 
. fertilization. It is here, therefore, where I join issue with him ; and it will be the main 
object of this paper to give positive evidence to show that there are decided advantages, 
rather than disadvantages, accruing to such plants as can, or rather do, habitually fer- 
tilize themselves. 
* Such an explanation of the nature of self-sterile plants is given by Mr. Darwin in his work on * Animals and 
Plants under Domestication,’ vol. ii. p. 140; but he appears to have now changed his views, for in ‘Cross and Self- 
fertilisation of Plants’ (p. 345) he says:—** When such plants [which are capable of complete self-fertilization] are 
taken to another country, and become in consequence self-sterile [as did Eschscholtzia in Brazil], their sexual 
elements and organs are so acted on as to be rendered too uniform [?]for such interaction [why not become too 
highly differentiated ?], like those of a self-fertilised plant long cultivated under the same conditions" [but such con- 
ditions do not render self-fertilizing plants self-sterile]. ; 
I cannot but think this change of view unfortunate ; for the earlier interpretation, to my mind, certainly carries 
more weight with it; for had such flowers been too little differentiated, it would imply they were under a more pri- 
mitive condition; and one would reasonably ie some correlative “ lowness" of structure elsewhere; but eh is 
far from being the case. : 
2¥2 
