I have also found that the visits of bees are necessary for the fertilisation of some kinds of clover; for instance twenty heads of Dutch clover (Trifolium repens) yielded 2,290 seeds, but twenty other heads, protected from bees, produced not one.

Again, 100 heads of red clover (T.

pratense) produced 2,700 seeds, but the same number of protected heads produced not a single seed.