172 MR. C. DARWIN ON THE SEXUAL RELATIONS OF 
croscope, and I found T could always (with one exception) distin- 
guish them : I then showed the specimens to two other persons, 
and they likewise distinguished the two kinds and pointed out 
which was the largest. The capsules of this form contain, on an 
average, 93 seeds: how this average was obtained will presently 
be explained. I repeatedly observed that the seed, when cleaned, 
seemed larger than that from the mid-styled or short-styled 
forms; consequently I placed 100 long-styled seeds in a good 
balance, and by the double method of weighing found that they 
equalled 121 seeds of the mid-styled and 142 of the short-styled ; 
or, in short, that five long-styled seeds equalled six mid-styled and 
seven short-styled seeds. These slight differences in the weight of 
the seed, and, as we shall soon see, in the average number produced, 
are worth recording, as they characterize not mere varieties but 
coexisting forms of the same species. 
Mid-styled form.—The pistil occupies the position represented 
in the diagram, with its extremity considerably, but in a variable 
degree, upturned ; the stigma is seated between the anthers of 
the long and the short stamens. The six longer stamens correspond 
in length with the pistil of the long-styled form ; their filaments 
are coloured bright pink; the anthers are dark-coloured, but 
from containing bright green pollen and from their early de- 
hiscence they appear emerald-green. Hence the general appear- 
ance of these stamens is remarkably dissimilar from that of the 
longer stamens of the long-styled form. The six shorter stamens, 
enclosed within the calyx, resemble in all respects the shorter 
stamens of the long-styled form, and both correspond in length 
with the short pistil of the short-styled form. The green pollen- 
grains of the longer stamens are plainly larger than the yellow 
pollen-grains of the shorter anthers: this fact was conspicuous in 
several camera-lucida drawings made for me by my son, Mr. W.E. 
Darwin. There is some variability in size, but „12, of an inch 
may be taken as about the average diameter of the green pollen- 
grains when distended with water, and 72,5 as the diameter of 
the yellow grains of the shorter stamens ; so that the difference 
in diameter is in about the proportion of four to three. The cap- 
sules contain, on an average, 132 seeds ; but, perhaps, as we shall 
see, this is rather too high an average. The seeds themselves are 
smaller than those of the long-styled form. 
Short-styled form.—The pistil is here very short, not one-third 
of the length of that of the long-styled form. It is enclosed 
within the calyx, which, differently from in the other two forms, 
