To Daniel Oliver   27 May [1861]¹

My dear Sir

Will you show this note to M^r Crocker & ask him if he is inclined to try a little experiment for me.—² Vinca major I believe never seeds in England & is said never to seed in Germany; & I find pollen so placed it could never get on stigma without insect aid.— I have pot of Vinca major & I have passed fine bristle between anthers (not cutting or touching the flowers) in same way as proboscis of moth would pass to nectary, near the sides of the corolla; pollen sticks to bristle & a bristle thus covered from pollen of one flower is used for another flower.— I did this & I have 4 or 5 fine pods swelling, whereas every other seed-vessel shanked off soon after corolla dropped.—³

Now will M^r Crocker do this (& it will not take him 2 minutes) for any exotic Vincas, which naturally have never seeded; mark the $\frac{1}{2}$ dozen flowers thus treated, & hereafter let me know whether pods swelled & whether seed was obtained.—

My apocynum (or fly-catcher) is coming up; I thought it was as dead as mutton: I have been trying Vinca in preparation for this Plant.—

You once told me that M^r Crocker liked experiments; if so I wish he would insert fine brush, like a Bee into a few exotic Polygalas which do not naturally seed & mark flowers & see if pods swell; I suspect they require insect agency. By the way you have not sent me P. farinosa; I daresay you have been so busy that you forgot it.—⁴

I beg & pray you not merely to acknowledge this.

Yours most sincerely | C. Darwin

I am surprised to find Cowslips utterly sterile without aid.— bears on origin of Oxlips.—⁵