Origin of Species Variorum

→ find from experiments 1861 1866 1869 1872

have, also, reason to believe 1859 1860

↑ 1 blocks not present in 1861 1866 1869 1872; present in 1859 1860

From experiments which I have tried, I have found that the visits of bees, if not indispensable, are at least highly beneficial to the fertilisation of our clovers; but humble-bees alone visit the common red clover (Trifolium pratense), as other bees cannot reach the nectar.

→ this 1861 1866

whether they could do so 1869 1872

→ being apparently not 1861 1866

not being 1869 1872

→ we may infer as highly probable 1861 1866 1869 1872

I have very little doubt, 1859 1860

→ two-thirds 1860 1861 1866 1869 1872

two thirds of 1859

pollen-masses and thus to fertilise them. I →find from experiments that humble-bees are

indispensable

almost indispensable

to the fertilisation of the heartsease (Viola tricolor), for other bees do not visit this flower. ↑ I have also found that the visits of bees are necessary for the fertilisation of some kinds of clover: for instance, 20 heads of Dutch clover (Trifolium repens) yielded 2,290

seeds;

seeds,

but 20 other heads protected from bees produced not one. Again, 100 heads of red clover (T. pratense)

pro- duced

produced

2,700 seeds, but the same number of protected heads produced not a single seed. Humble-bees alone visit red clover, as other bees cannot reach the nectar. It has been suggested that moths may

~~serve to~~

serve to

fertilise the clovers; but I doubt →this in the case of the red clover, from their weight →being apparently not sufficient to depress the

wing petals.

wing-petals.

Hence →we may infer as highly probable

that

that,

if the whole genus of humble-bees became extinct or very rare in England, the heartsease and red clover would become very rare, or wholly disappear. The number of humble-bees in any district depends in a great

measure

degree

on the number of field-mice, which destroy their combs and nests; and

Mr. H.

Col.

Newman, who has long attended to the habits of humble-bees, believes that "more than →two-thirds

them

of them

are thus destroyed all over England." Now the number of mice is largely dependent, as every one knows, on the number of cats; and

Mr. Newman

Col.Newman

Col. Newman

says, "Near villages and small towns I have found the nests of humble-bees more numerous than elsewhere, which I attribute to the

numbe

number

r of

cats that destroy the mice." Hence it is quite credible that the presence of a feline animal in large numbers in a district might determine, through the intervention first of mice and then of bees, the frequency of certain flowers in that district!

In the case of every species, many different checks,