4rOO 
AMERICAN AG-RICULTURIST. 
[J!hovkmbeh, 
roses—cited by Prof. C., we do not tbink he has 
made out a veiy strong argument. Still, a prop¬ 
osition coining from so high an authority de¬ 
serves respectful attention, and we allude to it 
as a topic likely to cause some discussion 
among horticulturists. Who knows but the case 
of our puzzling sweet and sour apple may 
serve help support Professor Caspary’s view ? 
Insects and Plant Fertilization. 
SIXTH ARTICLE. 
lu our foregoing iilustrations, insects are seen 
to carry the pollen of one flower to another 
e.vactly like it; or else to bear the pollen from a 
male flower to a female flower, belonging per¬ 
haps to a separate plant or tree, as in willows. 
In the present article we will call attention to a 
still dilferent case, 
viz., that of dimor¬ 
phous flowers. That 
is, where they are of 
two sorts, but both 
hermaphrodite. In¬ 
stances of this kind 
Fig. 1. — Flower of nous- 
tonla or Oldenlandia ccerulea; 
1 ( 1 , enlarged view of the same 
with the ovary or seed-vessel, 
cut half away, and the corol¬ 
la split down and laid open, 
showing the 4 stamens (an¬ 
thers) attached high up, while 
the style is short. 
are common enough; 
but, as we have room 
only for a single illus¬ 
tration, w'e will take 
for our example a 
pretty little spring 
flower which every 
body knows,or ought 
to know, the little 
Houstonia. Almost 
every wet pasture or 
meadow, or grassy 
bog, is decked in 
spring by these tiny 
flowers. They are all 
alike as to the corolla, and all hermaphrodite, 
having good stamens and a good pistil. But on 
inspection it may be seen that, while all the blos¬ 
soms of one clump are as in fig. 1, and show only 
the tips of the four anthers in the eye or throat, 
the style being short and included (see fig. la), all 
those of some other clumps will be as in fig. 2 
(seen dissected in fig. 2a), the four anthers out of 
sight low down in the tube of the flower, but 
the tip of the style with its two stigmas emerg¬ 
ing into view. There are, on the whole, about 
as many of one kind as 
of the other; and the 
seeds from the pod of 
either will produce 
plants of both sorts. 
Both sorts mature seeds 
freely. No. 1, the short- 
styled sort, may fertilize 
itself, as the pollen may 
drop from the bursting 
anthers upon the stigma 
underneath. The long- 
styled flower (No. 2), 
however, is not likely to 
be fertilized without 
help. Both are in fact 
fertilized by aid of in¬ 
sects, and the one sort is 
habitually fertilized by 
the other sort. How 
this is done, and how perfect the arrangement 
for doing it is, will be seen at a glance now that 
the thing is understood. If any small flying in¬ 
sect, with a proboscis about long enough to 
reach the bottom of the flower, should visit No. 
1, it will probably smear its face with some of 
the pollen of the anthers it comes in contact 
Fl;. 2.—Another flower of 
IToiistonla, ."ind 2a, .1 similar 
dissection of it; the style 
long and projecting, but 
the 4 anthers attached low 
down. ' 
with; and in passing to other blossoms of that 
sort, it can do little more than to transfer some 
of the pollen from one anther to another; 
though it is quite likely that some grains of pol¬ 
len, sticking to the proboscis, may be carried 
down to the stigma of the same or of the next 
flower. If the insect visits a succession of long- 
st 3 ded flowers, No. 2, it will rub its face repeat¬ 
edly upon the projecting stigmas, with a mere 
chance that a grain of pollen, extracted b}' the 
proboscis from one of the included anthers, may 
be dropped by the waj^ upon the stigma of the 
next flower. But suppose the insect passes 
from the short-styled flower. No. 1, to the long- 
styled, No. 2. Why, then the pollen which smears 
its face at No. 1, will be brushed off upon the 
stigmas of No. 2. And if the insect then pro¬ 
ceeds from No. 2 to a fresh No. 1, any pollen 
adhering to the proboscis from the anthers of 
the former, would be neatly transferred, most 
probably, to the corresponding stigmas of the 
short style of the latter; and so on. 
Here not only are individual flowers cross- 
fertilized, but the two sorts of flowers cross-fer¬ 
tilize ; and that is what the whole arrangement 
is evidently for. The flowers of the MitcheUa 
or Partridge-berry of our woods, which are 
produced about midsummer, are on the same 
plan. So are those of Primroses; and it was in 
the Primrose that this dimorphism was first de¬ 
tected, many j^ears ago; but the meaning of it 
was completely unknown until Mr. Darwin 
made it out four or five jmars ago. This capital 
investigator also showed that, not only are these 
flowers, of either sort, nearly barren when in¬ 
sects are excluded,—which might be expected, 
inasmuch as little or no pollen would reach the 
stigmas unaided,—but even that the pollen of 
either sort produced much less effect upon the 
stigmas of that sort than it did upon the stigmas 
of the other kind. Indeed, he found that in 
some such plants, the pollen which perfectly 
fertilized the other sort, would not act upon its 
own sort of stigma at all. This is so in the Red- 
flowered Flax, grown in our gardens for orna¬ 
ment, and to some extent in a Avild blue-flower¬ 
ed Flax; while the blossoms of the common field 
Flax are not dimorphous at all. All this clear¬ 
ly proves that in dimorphous flowers we have 
merely another way in which nature secures 
cross-fertilization ; and all the dimorphous flow¬ 
ers we know of are fertiiized by insect-agency. 
In folloAving up this subject, Mr. Darwin late¬ 
ly discovered that the blossoms of the Spiked 
Loose-strife {Lyfhrum Salicaria) are trimor- 
phous or of three sorts; and we may close this 
article with a very brief account of this curious 
case. From seeds of the same pod come three 
forms, in about equal numbers, viz.: 
1. —The long-styled form; which has 6 short 
stamens enclosed in the calyx, G mid-length 
stamens, protruding out of the calyx, and a 
style which is still longer (fig. 8). 
2. —The mid-length styled form, with G long 
and G short stamens. The stigma and the 
anthers of the long stamens of this and the last 
have changed places, (fig. 4) 
3. —The short-styled form, Avhich has G mid¬ 
length and G long stamens. The stigma in this 
answers, in position,to the anthers of the short 
stamens of the two preceding forms, its mid¬ 
length anthers to the stigma of one of the pre¬ 
ceding, and those of the long stamens to the 
stigma of the other. All the floAvers of any one 
plant arc alike. The three sorts of anthers have 
distinguishably different pollen; and each sort 
of pollen proves to bo more effective upon some 
other stigma than that of the same sort of floAver. 
Hero, in the hermaphrodite flowers of one and 
the same species, are three sets of males (and 
in function even five sets of males), and three 
Figs. 3, 4, 5.—Tlic three forms of Spiked Loose-strtf# 
(Lythrum Salicaria), oue side of the calyx cut away, and 
the petals taken off; 3, the long-styled and mid-length and 
short-stamened; 4, Avith mid-length style and long and short 
stamens; .5, Avith short style and mid-length and long sta¬ 
mens. The dotted lines and arrows shoAV the routes by 
which pollen Is effectively carried to stigmas by bees, etc. 
sets of females, about as distinct in action as if 
they belonged to so many distinct species. For 
Mr. Darwin has shown that only the longest 
stamens will fully fertilize the longest pistil, the 
middle stamens the middle pistil, and the 
shortest stamens the shortest pistil. Artificially 
Ave can make a dozen distinct crosses; but only 
those above mentioned, Avhieh experiment 
proves to be the most prolific, are very likely 
to be made in nature. And these are made 
thus : The flowers are visited by bees and the 
like. They invariably alight on the upper side 
of the flower, and insert their proboscides along 
the upper and inner magin of the calj'^x, where 
some room is conveniently left for the purpose, 
giving access to the bottom of the floAver. When 
the bee reaches with his proboscis the bottom of 
the flower, where the honey is found, the long 
stamens of figs. 4 and 5 rub against his abdomen, 
and sprinkle it Avith their pollen. Flying to the 
long-styled form (fig. 3), its stigma rubs against 
the same place and takes some of the pollen. 
The middle-length stamens (figs. 3 and 5) dust 
with their pollen the under side of the bee's 
thorax, between the front pair of legs; the stig¬ 
ma of the mid-length pistil (fig. 4) hits the same 
spot. The anthers of the short stamens (figs. 3 
and 4) are hit by the chin and the proboscis of 
the bees, the front of the head only being insert¬ 
ed into the throat of the calyx; and this sort 
of pollen only Avill be carried to the stigma of 
the short pistil (fig. 5), Avhich rubs in its turn 
upon the bee’s pollen-poAvdered chin. 
What advantage has this triple arrangement 
for crossing over the more common dimorphous 
plan ? Perhaps there is some economy in it or 
greater certainty of effective crossing. If, say 
only tAvo plants grew near each other, there is 
only an equal chance that they may be of dif¬ 
ferent forms, and so both fertile. But Avhen 
there are three sorts, each capable of fertilizing 
the other tAvo, the chanees are tAvo to one in 
favor of any two contiguous plants being of dif¬ 
ferent sorts and so both productive. A. G. 
