504 Meeting of the British Association. [Oct., 
“This was followed by his paper on the two well-known forms 
of the Primrose and Cowslip,* popularly known as the pin-eyed 
and thrum-eyed: these forms he showed to be sexual and com- 
plementary ; their diverse functions being to secure, by their 
routual action, full fertilization, which he proved could only take 
place through insect agency. In this paper he established the 
existence of homomorphic or legitimate, and heteromorphic or 
illegitimate unions amongst plants, and detailed some curious obser- 
vations on the structure of the pollen. The results of this, perhaps 
more than any other of Mr. Darwin’s papers, took botanists by 
surprise; the plants being so familiar, their two forms of flower so 
well known to every intelligent observer, and his explanation so 
simple. For. my own part I felt that my botanical knowledge of 
these homely plants had been but little deeper than Peter Bell’s, to 
whom 
‘ A primrose by the river’s brim 
A yellow primrose was to him, 
And it was nothing more.’ 
Analogous observations on the dimorphism of Flax and its allies, 
formed a subsequent paper ; during the course of which observations 
he made the wonderful discovery, that in the common flax, the 
pollen of one form of flower is absolutely impotent when applied to 
its own stigma, but invariably potent when applied to the stigma of 
the other form of flower; yet the pollens and stigmas of the two 
kinds are utterly undistinguishable under the highest powers of the 
microscope. 
‘“‘ His third investigation was a very long and laborious one on 
the Common Loosestrifef (Lythram Salicaria), which he showed 
to be trimorphic ; this one species having three kinds of flowers, all 
annually abundantly produced, and as different as if they belonged 
to different species; each flower has, further, three kinds of stamens, 
differing in form and function. We have in this plant, then, six 
kinds of pollen, of which five at least are essential to complete 
fertility, and three distinct forms of style. ‘To prove these various 
differences, and that the co-adaptation of all these stamens and pistils 
was essential to complete fertility, Mr. Darwin had to institute 
eighteen sets of observations, each consisting of twelve experiments, 
216 in all. Of the labour, care, and delicacy required to guard 
such experiments against the possibility of error, those alone can 
tell who experimentally know how difficult it is to hybridize a large 
flowered plant of simple form and structure. The results in this 
case, and in those of a number of allied plants experimented on at 
the same time, are such as the author's sagacity had predicted ; the 
* Journal of the Linnean Society of London,’ vol. vi., p. 77. 
+ ‘Journal of the Linnean Society,’ vol. vii., p. 69. 
+ Ib., vol. viii, p. 169. 
