The sun., 1888-10-28

out this book, all these effects are simply the
direct results OF the insects themsolves. The
guides. like obstructing tanges OF hair and
nectaries nre always exactly where the ir-
ritation would be set up, and | take them to
be one result OF u moro localized flow OF nutri-
ment to the positions in question. Instead,
therefore. OF a flower having just painted n
petal with n golden streak to invite the insect.
and TO show it tho right way Of entering, the
first insect visitors thems selves induced the
flower to do 1t and so benefited all future
comers."
In order further to support his doctrine OF
the origin OF the various attributes OF flowers
In response to direct stimuli, Prof. Henslow
brings forward the proved effect OF nutrition
alone upon their colors. 1t Is well known that
these vary much moro in garden earth than
when the plants are growing wild, showing
that tho Ingredients Of tho soil produce a dif-
ference in coloring A practical writer on such
subjects has observed that striped dahlias are
best preserved by planting them in poor SOIL
as whom planted In rich soil the color runs.
The vnriegated foliage OF pelarRonlums is said
to be affected in the samo way. 1t is affirmed
that alum turns hydrangeas blue. while phos-
phate OF iron or muriate OF ammonia appears
TO brighten the red tint. A self-colored camel
liza has been known to become striped on the
application of chloride of lime, and the use Of
ammonia will brighten the colors Of balsams.
The effect OF light Ia also most marked. Some
flowers change their colors in the course OF q
single day, apparently under the influence OF
the suns rays. There Is phlox which at
o'clock In the morning is light blue. but alters
as the sun grows stronger. until by 10 o'clock
II has assumed Its proper color. a bright pink.
The "Changeable Hibiscus" has flowers which
are white in the morning. mink at noon. and
bright red at sunset The flower OF the Cobra.
In the course OF its expansion. changes from
green to violet. Prof. Henslow also cites the
fact that the reproductive system OF plants is
known to be directly affected By the environ
ing condition. Temperature has marked In
nuence on the development of the sexes: the
male energy OF tho plant is stimulated by
heat, while the female develops moro strongly
In a relatively cool atmosphere. One observer
found that watermelons grown at n very high
temperature grew luxuriantly and produced q
profusion OF male blossoms. but no fruit The
same meexpermenter succeeded for many years In
making cucumber plants produce female flow
ers only by keeping them steadily at o low tenn
perature. With regard to the effects of nutrition
upon the Sexes 1t is quito generally admitted
that the female sex in plants is correlated with
relatively stronger vitality. In trees. In which
the two sexes are produced on separate shoots.
the stronger shoots produce the female flow
ers. and tho weaker the male Male flowers
are said not to appear on female maple tree
till its vital power is partially exhausted. lis
also common thing for some trees to change
their sex at different seasons or in different
places Some species which habtually bear
both sexes on the same plant have occasion
ally tendency to separate and bear the sexes
on different plants. Mr.. Darwin records that
" a tendency to the separation OF the sexes in
tho cultivated strawberry seems to be much
moro strongly marked in tho United States
than in Europe and this appears to be the re-
suit Of the direct action Of climate on the re-
productive organs" Muller gives two cases Of
another plant where it was apparently certain
that the soil was q chief cause OF the separa-
tion Of the sexes.
All the examples and arguments cited relate
only to the variations in floral structures.
but. theoretically. Prot. Hensow would &C.
count not oEly for the variations but for the
origin OF flowers. as We now know them. by
similar processes. And he would thus ac-
count not only for brilliant but also for insigni-
flcant blossoms. on the suppositon that all
flowers have first been called into existence by
insects. and that tho less showy blossoms, hav-
ing been subsequently. for some reason,
neglected have reverted to less attractive
condition. He is inclined to regard Gymnos-
perms rs the ancestors OF our modern Dlcoty-
ledens and having once assumed the existence
Of a leaf-bud some Of the members OF which
have already differentiated into carpellary
others into staminal organs. 1t is, he says. easy
to imagine that such primitive flower might
have been visited by insects for its pollen alone.
Having" says Prof. Henslow "once at
tracted insects to come regularly, then null
titudinous series OF differentations would fol-
low. The corolla would in all probability be the
first to issue out OF the bracts. being the next
whorl to the stamens. and as result OF stimu-
us other changes already described un-
ler the principles Of variation. would follow by
degrees and in different combinations: but in
every case they would be due to the responsive |
action Of the protoplasm in consequence Of the |
mutations set up by the weights. pressures. |
htrsts. tensions, &C.. OF the insect visitors.
Thus, then. do believe that the whole |
loral world has arisen"