334 REV. GEORGE HENSLOW ON THE 
* We thought Nature had a horror of in-and-in breeding. Our selected breeds of cattle are the 
result of this sort of selection, and they have proved just as healthy and productive as the veriest scrub. 
But it was thought they would at least revert to their original form when the hand of man was taken 
away. Prof. Brewer, however, showed that this was also a mistake **. Quite recently Mr. George Darwin 
has shown, in a remarkable paper, made up of an extensive study of old families among the English — 
nobility, where marriages among relations have been a source of social necessity for ages, that the popular ` 
idea is erroneous. These intermarriages have resulted as productively and as healthily, mentally and — 
morally, as the average marriages of the rest of the world” t. 
I am not in a position to be able to refute or endorse these latter remarks, upon which | 
I am not competent to form an opinion; though perhaps it is worthy of observation | 
that plants and vertebrate animals are not on a parallel stage of development; for the ` 
highest plant, by its composite character of powers of budding, each bud being prac- 
tically a new individual, would seem to be more on a level with a low invertebrate i 
animal; and therefore what may be true for the highest plants may be equally true for 1 
the lowest animals, though the highest of the vertebrates may be far from exhibiting ` 
similar or parallel phenomena with plants. : 
Respecting the general prevalence of self-fertilization in the vegetable kingdom, how- 
ever, I agree entirely with Mr. Meehan; and with reference to the immediate cause of ` 
self-fertility or sterility, I believe they are due to the existence of and want respectively | 
of what I would call homogamic equilibrium between the andreecium and gynecium, | 
at least as far as morphologically self-sterile plants are concerned. The peculiarities of ` 
pollen which is impotent upon the pistil of the same flower (that is, when the flower is - 
physiologically self-sterile) are too subtle for any analysis at present known, and can only | 
be described by the indefinite phrase of undue or excessive differentiation. 
What led me to arrive at the above conclusion was a series of observations on the | 
emergence and growth of the whorls of flowers. I found the following to be the usual 1 
order of development with flowers having conspicuous corollas. First, and invariably 80, 
appeared the sepals, which always grew to a size very considerably in advance of and 
much larger than the remaining organs. Secondly, the stamens opposite the sepals; 
and if there be two whorls, then the stamens opposite the petals. Thirdly, the pistil, and, — 
last of all, the corolla. It is, however, a matter of extreme difficulty to detect the exact | 
moment of the emergence or origin of the corolla; and in the majority of cases it pro- - 
bably emerges immediately after the calyx; but when this is the case, it seems to be 
immediately arrested, or at least the stamens grow so rapidly, the anthers enlarging, ` 
especially while every thing else is rudimentary, that the corolla is much delayed in com- 
parison with the stamens. It is not until the latter are nearly completed, and the pistil 
much advanced, that the corolla regains its power, and then rapidly enlarges. : 
On the other hand, with inconspicuous flowers, such as small-flowered Crucifere, the 
pistil may emerge simultaneously with or even before the stamens; and then it grows 
very rapidly, and matures its stigma either just before or synchronously with the dis- 
persion of the pollen. 
* Prof. Wrightson, of the Roy. Agr. Coll. Cirencester, informed me that in-breeding i is constant! pesto with 
short-horns, but with no deteriorating effects. d 
T ‘Gardeners’ Chronicle,’ Sept. 11, 1875. 
