384 SCIENCE OE GARDENING.
“ A e means used by nature to produce seed; and the use of tbe floral
envelopes, that is, o fth e calyx and corolla, is to protect the stamens and pistil duiing
*’T o T l AAe>“ ext to the wood, is the most important p ir t of a p la n t; not only on
accoum oi I s C e l o man and other animals, but °n “ oonm
tinii of the sDCcies. “ The fruit during its growth is supported at the
d r i e d t h e y will frequently he a whole yem^^ powers; othoi-s, as clover,
. when buried beyond « ™rt«” froPj? !™« g eA n a te , after having been
retain them, and when hioug p >,•/,>, ov/x nf>pp«!<?flrvfor the termination of seeds,
buried for many years. The conditrons wluch me ,oost favours
:rr* ^ 5.s?;a£«; S /j s it ’S*f a=i"S
in which a large quantity of ta r is ^ , ^ ^ is t eai-th rammed very hard, so as to
tection whatever. timTretaiA the vital
exclude the air,, is said to J® L preserve are those which contain much
S r ^ t L h e L » » “ * ^ case o A e seeds of the Brassica family, and
of musteffl and r e ? “ t e % m aL
but in different degrees Some o d om P P ^ tpg
rubbed ; some are most apparent m « ®“ X w a t e r In some of the orucifene,
latter case, the oil has been combined t w as to render its odour
and other orders, the oil is the case o fth e nightimperceptible,
while during " f * '? * '® 7 general, plants In hot countries
by the heat, as to he imperceptible in the day-time.
1075. The tastes o f plants arise from su g a r; from different acids; from volatile oils,
which produce an aciid ta s te ; from tannin, which produces astringcncy; and from a
mixture of mucilage with a little tannin, wliich produces what is called a herbaceous
taste.
1076. The vital principle o f plants seems to depend u p o n a degree of irritability which
exists in th em ; of a character analogous to that of animals, though far inferior in degree.
This is considered to be proved by tho action of mineral and vegetable poisons on plants.
M. Marcct, of Geneva, has found that mctalhc poisons act upon vegetables neai-ly as they
do upon animals; and that vegetable poisons also cause the death of plants. From this
it is infeiTcd, that plants have a system of organs analogous to the nerves of a.nimnk
S e c t. HI. Diseases o f Plants.
1077. Plants are subject to numerous diseases, the origin of the gi'cater part of which
is ahnost wholly unknown. Some, it is probable, arise from a derangement of the circulation
of the fluids; and others, from an undue absorption of water.
Tabes, o r Gangrene , is a term applied to a general languor of the system, under which the plant
withers away, or becomes rotten. In succulent plants, this or a similar disease is denominated Anasarca,
or Dropsy.
Scorching, o r In su la tio n , is produced by too high a temperature ; or, by excessive evaporation. A
variety of this disease is termed Marcor, or Welting.
Chlorosis, or E tiolation, is a kind of constitutional debility, supposed to depend on th e too great accumulation
of oxygen, from the absence of light, and from other causes. It is often produced from the
action of insects on th e roots.
Canker, o r Caries, exhibits itself in small brown dead spots, which extend on all sides of a branch
until they surround and kill it. The disease is continued by grafting, and no cure for it is yet known.
Carcinoma is a term given to the appearance of an unusual deposit o fth e cambium or returning sap
between tiie wood and the bark ; in this case, the cambium becomes putrid, and oozing out through the bark,
the latter separates from the alburnum, and th e intervening space forms a nidus for insects, which soon
destroy the tree.
E x tra va sa tio n , or G um m in g , is one of th e most common diseases of trees, and is known to most gardeners.
Galls are tumid excrescences, caused by the punctures of insects. Alburnitus is a term applied
to the appearance of a layer of soft wood, between layers of a wood of a harder texture, and is supposed
to arise from a wet season.
Albugo, F e rru g o , a n d Uredo, that is, mildew, rust, smut, brand, and blight, &c., are caused by the presence
of innumerable minute funguses, which are to plants what intestinal worms are to animals.
E rg o t, o r Clavus, is a brown or black excrescence from the seeds of grasses, not depending on a
parasitical fungus. T h e ergot of rye is used in medicine.
Spotting, o r Necrosis, consists of small black spots on the leaves and soft parts of plants, most probably
arising from wet and co ld ; since it is most common among exotics in cold seasons.
Melligo a n d S alsugo are natural exudations of the juices of certain p lan ts ; the former produces the
manna of the ash ; and the latter, a saline secretion of the same kind.
The n am i e c s s o f j a n um b o e c r o OJ f other otuer diseases aiseases m mAgkt ig n z be oe given; such sucn as suffocatio,sunocatio, or choking u p ; icterus,
or jaundice e ; ; p pernio,e rn io ,or chilblain wounds caused by ^ i...frosts ; exostosis,i-..--.-. or . . clubbing . 4.... . . of the roots ;.... crispatura, .
. .
o r curling,, &c. ; 'but, '
as no cure can be offered for them, and as, like all the preceding diseases, they are
only to b
e prevented by regimen, th e ir enumeration here would be of little service to the young
gardener.
S e c t. IV. Hybrid Plants.
1078. The power o f hybridising “ appears to be far more common in plants than in
animals; for while only a few animal mules are known, there is scarcely a genus of
domesticated plants in which this effect cannot be produced by the assistance of man, in
placing tho pollen of one species upon the stigma of another. I t is, however, in general,
only between nearly allied species that this intercourse can take place ; those which arc
widely different in stractui'e and constitution not being capable of any artiflcial union.
Thus, the different species of strawberry, of certain tribes of Pclargdnuun, and of Cucur-
bitaccaj, intermix with the greatest facility, there being a gi-eat accordance between
them in general stracture and constitution; but no one has ever succeeded in compelling
the pear to fertilise the apple, or the gooscbeny the cui-rant. And as species that ai*e
veiy dissimilar appear to have some natural impediment, which prevents thcir reciprocal
fertilisation, so does this obstacle, of whatever nature it may be, present an insuperable
bai' to the intercoui'se of different genera. All the stories that ai’c euiTcnt as to the intermixture
of oranges and pomegranates, of roses and black ciuTants, and tlie like, may,
therefore, be set down to pure invention.” (Lind. Introd. 1st ed. p. 302.)
1079. Hybrid plants are generally sterile, or at least become so after a few generations.
“ A mule plant may, however, be rendered fertile by the application of the
poUcn of either of its parents, in which case its offspring assumes the character of the
parent by which the pollen was supplied.” (Lind. Introd. to Botany, 4th cd. (1848),
vol. ii. p. 242.) Though, generally speaking, hybrids can only be obtained between
nearly allied species, “ it is, nevci'thcless, said, that bigcners, that is to say, mules between
different genera, have in some few cases been artificially obtained. Kblrcuter
obtained such between Malvaceous p la n ts ; Gaertner, between Datura and henbane and
tobacco ; Wiegman, between a garden bean and a lentil ; and there arc other
cases. I3ut all such productions were as short-lived and sickly as they were monstrous,”
(Ibid.)
1080. The cause o f the sterility o f mule plants. Dr. Lindlcy obsci*vcs, “ is at present