THE THREE FORMS OF LYTHRUM SALICARIA. 177 
stigma of each form pollen from the stamens of corresponding 
length ; and we shall presently see the importance of this adapta- 
tion. It must not, however, be supposed that the bees do not 
get more or less dusted all over with the several kinds of pollen ; 
they certainly do, as could be seen with the green pollen from 
the longest stamens. Moreover, a case will presently be given of 
a long-styled plant which grew absolutely by itself, and produced 
an abundance of capsules, which must have been fertilized by its 
own two kinds of pollen; but these capsules contained a very 
poor average of seed. Hence insects, and chiefly bees, act both 
as general carriers of pollen, and as special carriers of the right 
kind *. 
Variability.—Before passing on to more important topies, I 
must say a few words on this head. Wirtgen remarks f on the 
variability in the branching of the stem, in the length of the 
bractez, size of the petals, and in several other respects. The 
plants now growing in my garden have their leaves arranged op- 
positely, alternately, and in whorls of three, and differ greatly in 
shape. The stems of the plants bearing leaves in whorls are 
hexagonal; those of the other plants are quadrangular. But we 
are concerned only with the reproductive organs: the upward 
bending of the pistil is variable, and in a remarkable degree in 
the short-styled form, in which it is sometimes straight, some- 
times slightly curved, but generally upturned at right angles. 
The stigma of the long-styled pistil frequently has longer papill® 
or is rougher than that of the mid-styled, and this than that of 
the short-styled form ; but this character, though fixed and uni- 
form with the two forms of Primula, is here variable, and I have 
* In my paper on the two forms of Primula (Journal Proc. Linn. Soc. 1862, 
D 85) I stated that I had only occasionally seen humble-bes sucking the flowers 
of the Cowslip (P. veris). Since then I have had some beds in my garden 
containing nearly 700 plants, and these were incessantly visited by Bombus 
hortorum and B. muscorum. I caught some of these bees, and I found (as I 
had anticipated in my paper, p. 86) that a vast majority of the pollen-grains 
which adhered to the base of the proboscis were large-sized and had come from 
the long stamens of the short-styled form, and were thus placed ready to ferti- 
lize the stigma of the long-styled form. On the other hand, on the middle, and 
near the tip of the proboscis, a very large proportion of the pollen-grains were 
of the small size, and had come from the short stamens of the long-styled form. 
My son caught, also, a moth (Cueullia verbasci) hovering over the bed, and I 
found on its proboscis a similar distribution of the two kinds of pollen-grains. 
I give these facts as a further illustration of the importance of the relative 
lengths of the stamens and pistil. 
T Verhand. des naturhist. Vereins, 5. Jahrgang, 1848, S. 11, 13. x 
d 
