Peas and Clover 153 
as the Red Clover (7. pratense) and the White Clover 
(T. repens)—appear each to depend upon some special 
insect for fertilisation. 
Years ago, in The Origin of Species, Mr. Darwin 
told how he had experimented with bees and Clovers 
to ascertain how far the latter were dependent upon 
the former for fertilisation. He said: “Twenty heads 
of Dutch Clover (7. repens) yielded 2290 seeds, 
but twenty other heads protected from bees pro- 
duced not one. Again, 100 heads of Red Clover 
(T. pratense) produced 2700 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 fertilise the Clovers; but 
I doubt whether they could do so in the ease of the 
Red Clover, from their weight not being sufficient to 
depress the wing-petals. Hence we may inter as 
highly probable that, if the whole genus of humble- 
bees became extinct or very rare in England, the. . . 
Red Clover would become very rare, or wholly 
disappear. The number of humble-bees in any dis- 
trict depends in a great measure on the number of 
field-mice, which destroy their combs and nests; and 
Col. Newman, who has long attended to the habits of 
humble-bees, believes that ‘more than two-thirds 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 Col. Newman 
says, ‘Near villages and small towns I have found 
the nests of humble-bees more numerous than else- 
where, which I attribute to the number of cats that 
destroy the mice.’ Hence it is quite credible that 
