[Illustration: FIG. 124.--_Anisocarpous sympetalae_ (_Aggregatae_). _A_,
flowering branch of _Houstonia purpurea_, x 1 (_Rubiaceae_). _B_,
vertical section of a flower, x 2. _C_, fruit of bluets (_Houstonia
coerulea_), x 1. _D_, cross-section of the same. _E_, bedstraw,
_Galium_ (_Rubiaceae_), x 1/2. _F_, a single flower, x 2. _G_, flower of
arrow-wood, _Viburnum_ (_Caprifoliaceae_), x 2. _H_, the same, divided
vertically. _I_, flowering branch of trumpet honeysuckle, _Lonicera_
(_Caprifoliaceae_), x 1/2. _J_, a single flower, the upper part laid
open, x 1. _K_, diagram of the flower. _L_, part of the inflorescence
of valerian, _Valeriana_, (_Valerianeae_), x 1. _M_, young; _N_, older
flower, x 2. _O_, cross-section of the young fruit; one division of
the three contains a perfect seed, the others are crowded to one side
by its growth. _P_, inflorescence of teasel, _Dipsacus_ (_Dipsaceae_),
x 1/4. _fl._ flowers. _Q_, a single flower, x 1. _R_, the same, with the
corolla laid open.]

The various species of _Lobelia_, of which the splendid
cardinal-flower (_L. Cardinalis_) (Fig. 123, _E_) is one of the most
beautiful, represent the very characteristic family _Lobeliaceae_.
Their milky juice contains more or less marked poisonous properties.
The last family of the order is the gourd family (_Cucurbitaceae_),
represented by a few wild species, but best known by the many
cultivated varieties of melons, cucumbers, squashes, etc. They are
climbing or running plants, and provided with tendrils. The flowers
are usually unisexual, sometimes dioecious, but oftener monoecious
(Fig. 123, _I_).

[Illustration: FIG. 125.--_Anisocarpous sympetalae_ (_Aggregatae_).
Types of _Compositae_. _A_, inflorescence of Canada thistle
(_Cirsium_), x 1. _B_, vertical section of _A_. _r_, the receptacle or
enlarged end of the stem, to which the separate flowers are attached.
_C_, a single flower, x 2. _o_, the ovary. _p_, the "pappus" (calyx
lobes). _an._ the united anthers. _D_, the upper part of the stamens
and pistil, x 3: i, from a young flower; ii, from an older one. _an._
anthers. _gy._ pistil. _E_, ripe fruit, x 1. _F_, inflorescence of
may-weed (_Maruta_). The central part (disc) is occupied by perfect
tubular flowers (_G_), the flowers about the edge (rays) are sterile,
with the corolla much enlarged and white, x 2. _G_, a single flower
from the disc, x 3. _H_, inflorescence of dandelion (_Taraxacum_), the
flowers all alike, with strap-