such natural orders as the Labiata and Scrophulariacea for instance. In no other group, perhaps not even excepting the ingeniously constructed Orchidacea, do we find such a blended series of high development. First of all, their petals are not only united into one piece (gamopetalous), but the different parts have developed unequally, so that the shape of the flower is what botanists term irregular. Ot

FIG. 33. Fertilisation of Salvia. Showing bee sucking nectar, and how the connective would be disturbed so as to force down stamens on its back, just where the pistil (st) would be touched by the pollen.

these overgrown parts, the most important are those forming the arched hood, which protects both stamens and pistils from moisture, and the labium or lower enlarged petal, thrust forth for insects to light upon, as a kind of floral door-step. The latter is also frequently brightly ornamented to attract them as well. The colours of most of these Labiate flowers are blue or purplish-claimed by Dr. H. Müller as the latest evolved. But the manner in which the stamens

for coming down just on that part of the insect's back which would be

FIG. 35. (a) Flower of Frog's-mouth; (6) Flower of Figwort or Scrophularia, fertilised chiefly by wasps.

charged, before they can open and expand without fear of self-fertilisation, will not detract from our

FIG. 36.-Orchid flower.

i

admiration of the device.

The plan of keeping the cleft stigmatic surfaces of the pistil together is one common to many other orders, although perhaps best seen in the Saxifrages

and many of the Compositæ.

The floral machinery of the Orchids is well known since the publication of Darwin's celebrated I refer my readers to that wonderful work for proofs of the high floral sagacity these flowers have developed. The devices of

book on those plants.

Orchids all over the world are of the most ingenious character; insomuch that Darwin's matter-of-fact investigations, as recorded in his Various Contrivances by which Orchids are fertilised by Insects, read like a romance. The manner in which the pollengrains of Orchids are collected into two masses

FIG. 38.-Section of Orchid flower; (st stigmatic surface; (a) pollinia; (r) base of ditto.

(pollinia), in every species, indicates how successful this method must have proved. There is a common contrivance, adopted by species of Orchids far removed from each other by geographical distance, whereby these pollen masses are quickly detached from their little chambers when ripe, and attached, as by some kind of "diamond cement," to the heads of the insects visiting the flowers (a device the reader can experimentally imitate by carefully thrusting the conical point of a black-lead pencil down the throat

of an Orchid flower), so that such insects carry them to other Orchids where the sticky stigmatic surfaces tear off the pollen-grains for themselves. A full knowledge of the practice increases our admiration for these aristocrats of the floral world!

FIG. 39.

FIG. 41.

FIG. 40.

FIG. 39.-Flower of Orchis purpurea.
FIG. 40.--Flower of Orchis militaris.
FIG. 41.-Flower of Orchis simia.

The "Milkweeds". (Asclepiadacea) of America bear flowers which in some respects approach those of Orchids, both for their remarkably high organisation and structure. They proceed a stage farther than any others, except perhaps those of Apocynum, for they possess an apparatus which catches flies not adapted to fertilise their flowers, and holds them until they are dead. Two-winged flies are the greatest sufferers by this mechanism; and any one keeping Asclepiads in greenhouses will find such strangled flies in the grasp of the flowers at almost any time during the summer. We shall presently see how other plants keep away unwelcome guests by sagacious devices— the Asclepiads keep them off by real "spring-traps," ruthlessly and fatally employed, and not kept for mere threatening purposes.

The contrivances set up by flowers to ensure crossing are being found out almost every week, as investigation proceeds. In the works of Lubbock