446 LETTEES TO DAEWIX, 1843-1859 
plants I should say that a high development in the scale is 
indicated by special adaptations of organs to the discharge 
of functions, great deviations in those organs from the type 
upon which they are constructed. Thus Ranunculaceae 
are low in the scale because the floral organs are apt to run 
into one another and revert to the type (a leaf) on which 
they are constructed — because calyx and corolla are so 
often alike — stamens often reverting and the follicles present 
little deviation from a leaf folded on itself. Hence Mono- 
petalous flowers are higher than polypetalous, inferior 
ovaries a higher type than superior, Dicotyledons than 
Monocot, Exogens than Endogens, &c., &c. 
Darwin's answer is given in * More Letters,' i. 76 : the 
distinction he draws hes in the amount of morphological 
differentiation and the division of physiological labour. (See 
below, p. 463, letter of December 26, 1858.) 
Darwin had been making out various Grasses from book 
descriptions, and sent one that baffled him for identification. 
Richmond, Sunday. 
My dear Darwin, — Your grass appears to me to be 
Festuca fratensis, and agrees as ill with the descriptions as 
most plants appear to do. How on earth you have made 
out 30 grasses rightly is a mystery to me. You must have 
a marvellous tact for appreciating diagnoses. I am sure 
that I could not have done it. I very much rejoice at your 
feats, as it will afford us many subjects of interest in common 
when w^e meet again. I think that some structural points 
would interest you — as that of the inflorescence of Grasses. 
Amongst facts of interest which will one day be licked into 
shape pro or con species and migration, is that of the South 
Coast of Australia. I have just made a resume of the 
Australian Leguminosae, about 900 species. Of these some 
450 inhabit the South West Corner, Swan Eiver, &c., and 
about 300 the South East (New South Wales, &c.), but there 
are not 10 species common to both ! Now what can migra- 
tion be about, trans-water or trans-land ? — and what a 
busy time of it Dame Nature has had in making so many 
species, whether by creation or variation. 
I am busy at Indian Compositae. There are two very 
common English Thistles, a small one, Carduus acanthoides, 
