To J. D. Hooker   2 December 1868

My dear Hooker

It is a splendid scheme, & if you make only a beginning on a Flora, which shall serve as an index to all papers on curious points in the life-history of plants, you will do an inestimable good service.¹ Quite recently I was asked by a man how he c^d find out what was known on various biological points in our plants; & I answered that I knew of no such book, & that he might ask half a dozen botanists before one w^d chance to remember what had been published on this or that point.² Not long ago another man, who had been experimenting on the quasi-bulbs on the leaves of Cardamine wrote to me to complain that he c^d not find out what was known on the subject.³

It is almost certain that some early or even advanced students, if they found in their Flora a line or two on various curious points, with references for further investigation, would be led to make further observations. For instance a reference to the viscid threads emitted by the seeds of compositæ,—to the apparatus (if it has been described) by which oxalis spurts out its seeds,—to the sensitiveness of the young leaves of oxalis acetosella with reference to O. sensitiva.⁴ Under Latherus nissolia it w^d better to refer to my hypothetical explanation of the grass-like leaves than to nothing.⁵ Under a twining plant you might say that the upper part of the shoot steadily revolves with or against the sun, & so when it strikes against any object it twines to the right or left, as the case may be.⁶ If again references were given to the parasitism of Euphrasia &c how likely it w^d be that some young man w^d go on with the investigation;⁷ & so with endless other facts. I am quite enthusiastic about y^r idea; it is a grand idea to make a Flora a guide for knowledge already acquired & to be acquired. I have amused myself by speculating what an enormous number of subjects ought to be introduced into a Utopian Flora,—on the quickness of the germination of the seeds, on their means of dispersal, on the fertilization of the flower, & on a score of other points, about almost all of which we are profoundly ignorant. I am glad to read what you say about Bentham, for my inner consciousness tells me that he has run too many forms together.⁸ Should you care to see an elaborate German pamphlet by Herman Müller on the gradation & distinction of the forms of Epipactis & of Platanthera?⁹ It may be absurd in me to suggest, but I think you w^d find curious facts & references in Lecoq’s enormous book, in Vaucher’s 4 vols, in Hildebrand’s Geschlechter-Vertheilung & perhaps in Fournier de la Fecondation.¹⁰

I wish you all success in your gigantic undertaking; but what a pity you did not think of it 10 y^rs ago, so as to have accumulated references on all sorts of subjects. Depend upon it you will have started a new era in the Floras of various countries. I can well believe that M^rs Hooker¹¹ will be of the greatest possible use to you in lightening your labours & arranging your materials.

Yours affectionately | Chas. Darwin