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entirely unknown. Sometimes, indeed, a deficiency of pollen may be assigned ; but in
many cases there is no perceptible difference in the hcaJthincss of structure of the fertilising
organs of a mule plant, and of its parents. I know of no person who has
attempted to prove this by comparative anatomical obsciwations, except Professor
Henslow of Cambridge ; who in an excellent paper upon a hybrid Digitalis, investigated
anatomically tho conditions of the stamens and pistilliiin, both of his hybrid and its two
parents, with groat care and skill. The result of his inquiiy was, that no appreciable
difference could be detected. Although the poivcr of creating mule plants, that are fertile
for two or tlu’cc generations, incontestably exists, yet in wild nature hybrid varieties
are far from common ; or, at least, there arc few well attested instances of the fiict.
Among the most remarkable cases ai-c, the Cistus Xcdon constantly produced between
C. monspcRsulanus and /aurifolius and Cistus longifolius between C. monspessulanus
and /jopulifolius, in the wood of Eontfroidc, near Nai-bonne, mentioned by Mr. Bcntham.
Again, the same acute botanist ascertained that Niixiiraga lùteopurpùrea of Lapeyrouse,
and N. ambigua of De Candolle, arc only wild accidental hybrids between S. aretiol</e.s
and calyciflora : they arc only found when the two parents grow together ; but there
they form a suite of intenncdiiite states between the two. Gentians, hainng a similar
origin, have also been remarked upon the mountains of Euroj^e. I t is difficult not to
believe that a great number of the reputed species of Nàlix, Fosa, Fùbus, and other
intricate genera, have also had a hybrid origin ; but I am not aware that there is at
present any positive proof of this.” (Lind. Introd., 1st ed. p. 304.)
1081. J ’he power o f obtaining mule varieties by art, Dr. Lindley continues, “ is, in a
practical point of view, I am inclined to believe, one of the most important means that
man possesses of modifying the works of nature, and of rendering them better adapted
to bis purposes. In om- gai'dens some of the most beautiful flowers have such an origin ;
as, for instance, the roses obtained between R . índica and moschata, the different mule
Potcntilhc and Càcteoe, the splendid azaleas raised between A. póntica and A. nudifiora
coccínea, and the magnificent Amcrican-East-Indian rhododendrons. By crossing varieties
of the same species, the races of fraits and of culinary vegetables have been brought
to a state as nearly approaching perfection as wc can suppose possible. A n d if simüm’
improvements have not taken place in a more important department, namely, the trees
that afford us timber, our experience as fully waiTants our entertaining the belief, tbat if
proper means were adopted, improved varieties of as mucli consequence might be introduced
into our forests, as have already been created for our gardens. In conducting
experiments of this kind, it is well to know that, in general, the characters of the female
parent predominate in the flowers and paits of fructification ; while the foiiagc and
general constitution are generally those of tho male parent. Thus, in the celebrated
Ahododendron álta-clcrénse, gained by Lord Cacrnaiwon by fertilising R . ai’borcum with
R . catawbicnse, the mule vai'iety had tho flowers and colom* of R. arboreiim, but more
the leaves and hai'dincss of constitution of R . catawbicnse.” (Ibid. p. 304.)
S e c t. V. O f the Metamorphoses o f Plants.
1082. Morphology or the gradual transmutation of leaves into the vai'ious organs of
a plant, is a subject which has lately engaged the attention of botanists. The first ideas
of this metamorphosis appear to have originated with Linnæus ; and the first attempt
to reduce it to a system with the poet Goethe, in the year 1790. According to this doctrine,
the bractcæ arc leaves affected by the vicinity of the fractification ; the calyx and
the corolla arc formed by the adhesion and vcrticillation of leaves; the filament is a form
of a petiole, the anthers of laminæ, and the ovarium itself a convolute leaf. Tlio
elementary organs used by nature in the constmction of plants being essentially tho
same, and the plan ui^on which they ai*e combined being cvei*y where uniform, it foUows
that the functions of plants are equally regular, and that evci'y thing which takes place
in the vegetable world is governed by a few simple laws. "Wiatever can be demonstrated
of one branch of a tree, is not only trae of all other branches of the same tree-,
but also of the branches of all other trees. Wliatevcr can be shown to govern the
structure of ono individual will also govern that of all other individuals.
1083. Stipuloe and bracteoe arc not uncommonly found transformed into leaves, in the
rose fmnily more especially ; hence these organs are considered as radimentai-y leaves.
Instances in which the calyx and even the corolla havo been transformed into leaves, as
ill tlie daisy, the tulip, the rose, &c., are familiar to evei-y gardener ; and hence it is
concluded that these organs also arc but modified leaves. In double flowers, every one
knows that the stamens are changed into petals ; but petals having been proved to bo
leaves, it follows also that stamens arc leaves, which is occasionally seen to be the case
in monstrous flowers. From these, and similar facts and arguments, Dr. Lindley
concludes, that “ there can be no difficulty in admitting the following propositions as tho
basis of morphology.”
b ftfo g .- ilte g e th c r a f low e r b u d , a n d f low e r b u d s
b r a e te o l e , is a m e t am o r p h o s e d b r a n c h c o r o ll a r y , t i i a t e v e r y f low e r , w i th i t s p e d ic u le a n d
r ‘ - ™
o r m e t am o r p h o s e d l e a v o r w h i d ” c o í S t i S r b í r é t e ' S o r a l m T t e m s a m f ' r o ™ ? [ “ » ' " ' “ ‘ “ ■'y
tlm s am e taw s o t a r r a n g e m e h t a s r c g u l a d j t e rm e d W e s r é r o í S ^ ' ^ r é S ^ ^ S
1084. All plants are alUm subject to metamorphosis. Tlie extent of the chanees which
they are capable of untlcrgomg may depend ou thcir constitutional poculiariticf and also
t L re ™ ? ®“ * “ fr The dcvclopemlnt of a S n T fn S
native habitation will, m general, rcmam unchanged; but tho same iilant in a state of
culture may undergo a considerable alteration in its external characters! This is tlie
L Z L c e - T “ “ " Sdi'don plauts arc and IS called, by botanists, irregular mctamoiiihosis. continually A t i I^
108.5. Metaimrffioses o f fr u it arc common both as to colour, flavonr, size smell and
stracture ; and tins is not only the case with fraits, popularly so «died, t a t ™ h sotas
and seed pods. In the gai-den pea, the pai-oliment-like lining of the pod occasionallv
dis.appear.s, and the entire substance becomes a lax, colluhu- substance
108 6. Pcrmanenaj o f metamorphoses. “ It is a general law of natu'rc, that seeds will
pcipetuato a species but not a variety; .and this is no doubt trae, if rightly considered ■
aLndd Cagrui ccuildtmt eis tIs, “ffo r many ye“afrts been u“n"cfeta s‘i“nfgt ly carried on kfrnoomw ng eton egraartidoenn etro!
p n c ra tio n without change ? The long red, and romid white r.adishcs oltahoLmikcts
io\vL L ’TLft ft" ■“''^■“ '““ ‘' “ ft ‘“ memoriid in the same state in which the?
noiv exist. The aiis-ivcr is this. A species will perpetuate itself from seed for ever
uiidci any cu-ciunstanccs, and left to tho simple aid of natm-c : but accidental varieties
c.annot bo so pei-pctuated ; if suffered to become wild, they very soon revert to the form
from which they originally sprang. It is necessai-y that they should be cultivated with
tho utmost care that seed should be saved from those individuals only in which the
marks of the variety are most distinctly tra c ed ; and all plants that indicate any disposi-
t on to cast off then- peculiar characteristics should ho rejected. I f this is carefully done
the existence of any variety of animal or perennial plant may undoubtedly be prolonged
Uiroiigh many genoi-ations ; but in woody plants this scarcely happens, it being a Lro
““ft''“ft" "ft'ft-ft^ Y
Vegetable Geography and Histonj, <
Chap. VH.
’ the Distribution o f Vegetables relatively to the Earth
and to Man.
1087. The science o f the distrihition o f plants is comparatively of recent date. “ In
ti e earliest days of botany,” says Sclilciden, “ in cvci-y description of a plant was noted
the place where it was found ; but no one anticipated that these notices enclosed the
p im of a new science.” A t last, Tournefort made a journey to the Levant, and when
Jic ascended Mount Ararat, it strack hhn that in the gradual elevation of the mountain
above the level of the sea, the vegetation assumed essentially different characters and
that these changes corresponded very closely with what he had observed in the vcircta-
tions of the moimtains iu his progi-ess from Asia Minor to Lapland. Tliis was a new
idea started, which was eagerly caught at by the botanists of that day. Soon after
Adanson discovered the fact, that umbelliferous plants seldom, if ever, occurred within
tiic trepics. In 1807 appeared Humboldt’s Essai sur la Géographie des Plantes, in which
an attcmpt was first made “ to bring tho observed peculiarities in the distribution of
vegetables into connection with the specialities of the climate.” Ten years later, Ilum-
holdt made a farther advance, and “ comprehending tlic whole earth in one intelligent
giancc, lie made the geography of plants part of a theoiy of tho earth ; and showed the
dependence of the distribution of plants—on a gi-cat scale as well as on a small one—unon
the physical qualities of the globe.” (Schleiden’s Plant (1848), p. 239.)
S e c t. I. Geographical Disti'ibution o f Vegetables.
1088. The territorial limits to vegetation ai'c dctei-ramed in general by three different
caiises : — 1 By sandy deserts, which seeds cannot pass over citlior by means of winds
H -'ft 1 r Sidiai-a, in Africa ; 2. By seas too vast for tlic seeds, of plants to he
uintoa irom one shore to the other, as in the ocean ; whilo the McditeiTaiican sea, on tho
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