This family is chiefly composed of shrubs, less frequently of small
trees, or perennial herbs; their leaves are undivided, most frequently
evergreen, stiff and leathery, and always without stipules. The flowers
are ☿ and _regular_, rarely slightly zygomorphic, most frequently
obdiplostemonous, and 4- or 5-merous through all the 5 whorls. _The
stamens are attached to the receptacle_, and as a rule are quite
free from the petals, an attachment which is very rare among the
Gamopetalæ. They have a simple gynœceum with _one_ undivided style, a
commissural stigma, and a _multilocular_ ovary, whose axile placentæ
project considerably into the loculi, and bear a large number of
ovules. ~The placentæ are sometimes not united, and in consequence, the
ovary is 1-locular with incomplete partition-walls, _e.g._ _Pyrola_,
_Monotropa_.~ Embryo straight, with endosperm. _The carpels are placed
opposite the petals._
The _diagram_ is generally Sn, Pn, An + n, Gn, in which n is 4 or 5. To
this may be added, that the _corolla is in most cases gamopetalous_,
but in some (especially _Pyrolaceæ_) perfectly polypetalous; and that
the _anthers usually open by pores_, and often have _two horn-like_
appendages (hence the name “Bicornes”) (Figs. 545, 546); frequently
the two halves of the anther are also widely separated from each other
at the upper end, so that the pores are placed each one at the end of
its own tube (Fig. 546); the pollen-grains in the majority are united
into _tetrads_ (Fig. 542 _D_).--The flowers, as a rule, are pendulous
and borne in racemes, coloured (red or white), but odourless. When the
fruit is a capsule, the placenta with the seeds attached persists as a
central column. A _mycorhiza_ occurs on many.
The majority of plants belonging to this family inhabit cold and
temperate countries, or high mountains in tropical regions; they prefer
cold and dry or damp places (bogs, heaths, etc.). Plentiful in N.
America.
Order 1. =Pyrolaceæ.= Perennial _herbs_; _petals most frequently
quite free from each other_, and falling off singly after flowering;
_the anthers are without appendages_, and open by pores (Fig. 544),
or by a transverse slit. The placentæ are thick. The seeds in the
_capsule-like_ fruit (loculicidal dehiscence) are exceedingly small and
light, they have a sac-like testa which loosely envelops them, an oily
endosperm, and an _extremely simple embryo_, which consists only of an
ellipsoidal, cellular mass, without cotyledons or differentiation into
plumule and radicle.
_Pyrola_ (Winter-green) is green, and has also large evergreen
foliage-leaves. The flowers, 5-merous, are most frequently borne in
racemes without a terminal flower; the anthers are extrorse in the bud
with the pores in the lower portion (Fig. 544 _A_), but they become
inverted at a later period, so that the pores open at the top (Fig.
544 _C_). ~_P. uniflora_ has a single, terminal flower; it winters by
its roots, producing from these in the spring aerial, quite unbranched
shoots. _Chimaphila umbellata._~
[Illustration: FIG. 544.--_Pyrola minor_: _A_ portions of a
young flower; _B_ the stigma; _C_ portions of an older flower
(longitudinal section).]
_Monotropa_ (Yellow Bird’s-nest) is very pale yellow, without
chlorophyll, succulent, and has only scale-like leaves closely pressed
upon the stem; it is a saprophyte. The raceme has a terminal flower,
and is pendulous before flowering. The anthers open by a semicircular,
transverse cleft. ~_M. hypopitys_ reproduces chiefly by root-shoots.~
About 30 species, especially N. Europe, N. America, and N. Asia.
Order 2. =Ericaceæ.= The flower (Fig. 545) is _hypogynous_, the median
sepal posterior; corolla, _gamopetalous_; the stamens are generally
_2-horned_, and the fruit is a _capsule_, less frequently a berry or
drupe. At the base of the ovary is a nectar-secreting disc (Fig. 545
_B_). This order comprises shrubs or undershrubs (rarely small trees),
which are evergreen, and as a rule have densely crowded leaves.
=1.= ERICEÆ, HEATH GROUP. Flowers most frequently _4-merous_ (S4,
P4, A4 + 4, G4, united in a 4-locular gynœceum), rarely 5-merous.
The withered corolla _persists_ after flowering. The leaves are most
frequently acicular, opposite or verticillate; the buds are without
scales. The fruit is a capsule.--_Calluna_ (_C. vulgaris_, Ling) has
a deeply 4-cleft corolla, which is less than the coloured calyx;
capsule with septicidal dehiscence.--_Erica_ (about 420 species; _E.
tetralix_, Cross-leaved Heath) has a tubular or bell-shaped, 4-dentate
corolla, which is much longer than the calyx. Capsule with loculicidal
dehiscence.--_Pentapera._
=2.= ANDROMEDEÆ. The flowers are 5-merous (S5, P5, A5 + 5, G5),
with _deciduous_ corolla. Capsule with loculicidal dehiscence. The
leaves are scattered, and incline more to the ordinary broad-leaved
forms.--_Andromeda_; _Gaultheria_; _Cassandra (Lyonia)_; _Cassiope_.
[Illustration: FIG. 545.--_Arctostaphylos uva-ursi._]
=3.= ARBUTEÆ. The flowers as in the preceding group (Fig. 545), but the
fruit is a berry or drupe. _Arctostaphylos_ (_A. uva-ursi_, Bear-berry)
has a drupe with 5 stones in a dry, farinaceous pulp; in other
species there is 1 stone with several loculi. _Arbutus_ (_A. unedo_,
Strawberry-tree) has a spherical berry.
_Pollination_ is effected by means of insects, especially by
bees. The pollen is light and dry, and is shaken out through
the pores of the anthers when the insects agitate the horn-like
appendages during their visits. Self-pollination takes place,
no doubt, in many cases.--800 species; the very large genus,
_Erica_, especially in S. Africa (the Cape).--OFFICINAL: the
leaves of _Arctostaphylos uva ursi_. _Arbutus unedo_ (S. Europe)
has an edible, peculiarly warted (strawberry-like) fruit. Many
_Erica_-species are cultivated as ornamental plants.
Order 3. =Rhodoraceæ= (=Rhododendrons=). This differs from the
preceding order in the _median sepal being anterior_, and hence the
position of the other floral whorls is also reversed. The flower is
_hypogynous_, in most cases 5-merous; the corolla is most frequently
deeply cleft or polypetalous, and falls off after flowering; the
anthers open by pores, and have _no horn-like appendages_. _Capsule_
with _septicidal_ dehiscence.--The shrubs or small trees belonging to
this order have, like the Vaccineæ, ordinary foliage-leaves, and the
buds are generally provided with _large bud-scales_.
_Rhododendron_ has 10 stamens, and a slightly zygomorphic flower with
deeply 5-cleft corolla (the section _Azalea_ has frequently only 5
stamens, the petal-stamens being absent). They are Alpine plants (200
species) in the mountains of Asia, especially the Himalayas; some in
S. Europe.--_Menziesia._--_Ledum_; small, rusty-brown, hairy shrubs
with polypetalous, expanded, star-like corolla.--_Kalmia_ (N. Am.) has
a cupular corolla, with 10 small, pocket-like depressions in which
the anthers are concealed until the arched, elastic filaments are
freed from this position by means of the insects, when they quickly
straighten themselves in the centre of the flower.--_Phyllodoce_;
_Loiseleuria_ (5 stamens); (_Clethra_ (?); also placed among the
Ternstrœmiaceæ).
About 270 species. Several species are ornamental plants.
Several plants of the order are more or less _narcotic_. _Ledum
palustre_ has been used as a substitute for hops.
Order 4. =Diapensiaceæ.= Hypogynous flower. 3 floral-leaves
beneath the flower (S5, P5, A5 + 0, G3). Stamens on the throat
of the corolla. Pollen-grains single. Disc absent. Capsule
loculicidal.--9 species from the Arctic regions. It is doubtful
whether this order should be included in the Bicornes; perhaps
it would be more correctly assigned to the _Polemoniaceæ_.
Order 5. =Epacridaceæ.= This order comprises those species of
the family which are confined to Australia and the South Sea
Islands. They are shrub-like plants, resembling the Ericaceæ in
habit, in the inflorescence, and in the structure, form, and
colour of the flower. They differ especially in having only
1 _whorl of stamens_ (placed opposite the sepals) and in the
anthers having only 2 loculi, and opening by a longitudinal
slit. Fruit most frequently a drupe (or loculicidal capsule).
_Epacris_-and _Styphelia_-species are ornamental plants. About
325 species.
Order 6. =Vacciniaceæ= (=Bilberries=). _The flower_ (Fig. 546) _is
epigynous, the corolla gamopetalous_, and _the fruit a berry_. The
latter is most frequently spherical, and bears on its apex the calyx,
which is generally very low, almost entire, and with a _disc-like
expansion_ inside. The flower is 4- or 5-merous (Fig. 546 _B_, _D_). The
anthers have 2 pores, and are most frequently 2-horned (Fig. 546 _F_,
_G_). Small shrubs; the leaves are scattered, not needle-like.
_Vaccinium_ (Bilberry, Whortleberry) has an urceolate, gamopetalous,
only slightly dentate corolla, and horn-like appendages to the anthers
(Fig. 546). ~_V. vitis idæa_ (Cowberry) is evergreen, with flowers in
racemes, and bright red berries; _V. myrtillus_ (Bilberry) and _V.
uliginosum_ (Bog Whortleberry) both have black berries with a blue
bloom, leaves deciduous.~--_Oxycoccus_ has a _polypetalous_ corolla
with the petals projecting backwards. Anthers without appendages. ~_O.
palustris_ (Cranberry) has a slender, creeping stem, and is evergreen.
Dark red berry.~
Pollination essentially the same as the preceding order.--320
species; especially in N. Am. Some are useful on account of
their edible fruits, especially _Vaccinium myrtillus_ and _V.
vitis-idæa_, and in a less degree _Oxycoccus_, etc. The fruits
of _V. myrtillus_ are _officinal_.
[Illustration: FIG. 546.--_Vaccinium uliginosum_ (var.
_microphyllum_). The parts of the flower _A-E_ are enlarged 5–6
times; _C_ and _E_ are longitudinal sections; _B_ and _D_ the
flower seen from above; _F_ and _G_ a stamen seen from the back
and front; _H_ the style and stigma.]