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etc.; whilst others, as

the Graminacea, Eri

caceae, Malvacea, Cruciferæ, etc., are exempt. There are, nevertheless, very few orders of phanerogamous plants in which some one or more species, belonging to this section of Coniomycetes, may not be found; and the same foster-plant will occasionally nurture several forms. Recent investigations tend to confirm the distinct specific characters of the species found on different plants, and to prove that the parasite of one host will not vegetate upon another however closely allied."

Dr. Cooke very generously and euphoniously speaks of the particular kinds of

FIG. 90.-d, two uredo spores of the Puccinia graminis germinating upon the cuticle of a wheat leaf; the germ-tube of the lower spore has just entered a stomatum; in the upper spore the process is more advanced.

plants whose life-histories he has studied with so

much diligence and success, in a tender and even affectionate manner. The victims are called "hosts" or "foster-plants;" but it is not difficult to see that all they get by their generous hospitality in entertaining such pests is robbery and murder, and that they are only "foster-plants" in the sense that the bird was foster-mother to the serpent's eggs which ancient fable says were placed under her to hatch, and whose successful result was to issue forth and destroy the pseudo-parent!

Our mildews, rusts, smuts, potato, vine, hollyhock, and other diseases, our pea-blights, roseblights, etc., only too surely proclaim the successful depredations of these vegetable barbarians, strong in their numbers and ferocity, like those hordes of Goths and Huns who burst like a flood upon and overcame the high civilisation of ancient Rome.

CHAPTER XIII.

"TURNING THE TABLES."

THE crimes of "robbery and murder," as illustrated by plant-life in the preceding chapter, were entirely confined to the vegetable kingdom. Nothing was there said of the fact that many plants are so virulently poisonous as to cause death to animals—that peculiarity has been already considered as protective. Nor have the habits of such wonderful and highly-elaborated pieces of vegetable mechanism as the Venus' Fly-trap (Dionæa muscipula), the Sundews (Drosera), the Pitcher-plants (Sarracenia, Nepenthes, Cephalotus, etc.), or of our humbler Butterworts (Pinguicula), been mentioned particularly as cunningly devised machinery for insect-assassination.

But it now remains for me to relate the strange means by which certain kinds of plants have been able to turn the tables" on their ancient and hereditary foes the insects. The latter serve the plants many a good turn, it is true-as when they are engaged in fertilising their flowers; but this

S

is performed by a few only out of the innumerable hosts of insects; and even the larva of the former make the leaves of the plants, whose flowers are benefited by their parents, pay fine and toll for the

service.

It may be that the remarkable habit of catching flies, and afterwards of making a meal of them, has been developed by adversity. I pointed out six years ago, in Flowers: their Origin, etc., that "The marsh-loving habits of most of these plants, both / British and foreign, show that they usually grow in places where their roots can absorb but little if any nitrogenous material. This duty is therefore thrown upon other parts of the plant, some of which are normally in the condition that the spongioles of the roots are; so that when decomposing animal matter comes into contact with them, they can absorb it." To the difficulty which marsh-plants have of getting nitrogen might be added that of obtaining potash and other salts, with which, however, captured insects would provide them. Our English Sundews (Drosera) may often be seen growing in myriads on the surface of Sphagnum bogs, their slender roots merely anchoring them to their places, and perhaps providing them with water; whilst the marvellously altered and adapted leaves not only obtain carbon from the atmosphere, but artfully contrive to get all the nitrogen, potash, etc., the whole plant requires from the capture of insects!

Such plants have been called "insectivorous" and also "carnivorous." Darwin has demonstrated that those fed with animal food produced more flowers and seeds than those left alone. There can be no doubt, therefore, that this habit is a highlyspecialised one, and that it has been acquired, for it is practised in varying degrees - from occasional indulgence to absolute necessity. And what is very striking is the manner with which fly-catching and digesting has been adopted by plants of various orders, in several ways, all over the world. Some of these set regular traps, like the Sundews, Venus' Fly-catcher, etc.; others, like our Butterworts, grease their leaves and curl up their edges. Many kinds in America grow specialised pitcher-shaped leaves, and smear their upper surfaces with a honey-like secretion, whose sweetness is intensified within, alluring the unsuspecting flies on until they cannot return. They then accumulate in a seething, filthy, half-dead, half-living mass, within the interior of this diabolically contrived trap-a mere manure-heap for the benefit of the plant, whose seeds will be all the richer in albumen from the transformation of the organic matter of the insects by the process of vegetable digestion or assimilation.

When members of the same genus of plants are found in various parts of the world practising the same habits, with such a remarkably similar mechanism, there is only one explanation I know of

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