My dear Bentham

Your letter of the 26^th is very valuable to me. Oxalis & ægiphilos seem capital cases. I will follow your suggestion about violets & today had several plants put into my experimental garden: I have attended & experimented on the regular flowers of Viola: they require insect-aid for at all perfect fertility; & as insects do not freely visit them, I have always supposed that the imperfect flowers produced seeds by parthenogenesis to keep the stock up; but I will attend to this subject next summer.—²

Thymus is a different case from Primula: some individuals being hermaphrodite & some female by abortion of anthers. In the English Thyme this abortion to a certain limited extent depends on growing in dry stations (I counted hundreds of plants).³ The garden Thyme seems to produce both forms irrespective of conditions. The female plants of the garden thyme produce nearly double the weight of seed, compared with the Hermaphrodites: the wild English female Thyme produces more than double the weight.— There is a slight difference in the stigmatic tissue in the Hermaphrodite & Female plants.— As you seem interested in dimorphic plants, I thought that perhaps you would like to hear these details.—

Since the above was written I have received your list of Oxalis, for which very many thanks.—⁴

Pray believe me— Yours sincerely & obliged | Ch. Darwin