Most Mistletoes and Loranthus have their own green leaves, and only take from the plant to which they are attached sap and mineral salts. But in Chile there is a beautiful Loranthus that has practically no green leaves at all. Its blood-red flowers grow in dense masses upon the giant Cactus, which is common on the drier hills, and these are always mistaken for the Cactus's own flowers, which are quite different. These almost leafless Loranthus, and the curious Arceuthobium are more parasitic than ordinary mistletoes, for they obviously take other food material (probably sugar and albuminoids) from their "host."
Another series of parasites or cannibals are quite common in Great Britain. One often sees in some meadow that the grasses are growing in a scanty and unhealthy manner; one then notices amongst them numbers of the Yellow Rattle or the Eyebright (which the Germans call Milk-thief). These plants are not very remarkable in any way, but if one examines them closely one sees that the leaves and stems are more purplish-red than is at all usual with our ordinary flowering plants. But if you dig up some specimens very carefully, then the wickedness of the Yellow Rattle and Eyebright becomes apparent; every here and there upon their roots are little whitish swellings which are firmly attached to the roots of other plants (generally of grasses). These two robber plants send from these swellings minute sucker-roots which pierce into the grass-root and intercept the water which the grass has been absorbing for itself.
They are therefore parasites, and indeed they may cause a considerable loss of forage in a meadow.
A good many other British plants are root thieves. Besides these two, there are the Cow-wheat, Red Rattles, Toadflax, Broomrapes, and Toothwort.
A curious point about them is that they differ amongst themselves in the degree in which they are dependent on the work of others. Some are able to grow quite well without any such extraneous help, but the Broomrape and Toothwort are entirely dependent on others' labours. They have extremely little chlorophyll and very small leaves, and are clearly parasites "pure and simple."
There are about 180 species of Broomrape (Orobanche). All of them attack roots, and most confine their attentions to one particular flowering plant. Their colours are generally very striking and unusual. Our British species are reddish, flesh-coloured, or dirty white, but some of the foreign kinds are blue or violet, yellow, or yellowish to dark brown. Generally the seedling Broomrape worms its way down into the earth till its root-tip touches the root of its special favourite host, then the root of the Broomrape fixes itself for life; its suckers grow into the host and absorb all the food material which it requires. Those kinds which attack Tobacco and Hemp are dangerous pests and do considerable damage.
The Toothwort (Lathraea) is so called because its scales have a sort of resemblance to human teeth. With the curious superstition which prevailed in medieval times, it was supposed that the plant must be a remedy for toothache because it resembled teeth. Unfortunately this is not the case.
It is, generally, quite like the Broomrape in its method of growth, but it sends out long thread-like branching roots with suckers on the ends, which become fastened on the Hazel roots. For several years the plant remains underground and forms very odd-looking, white, scaly branches. These scales are rolled back in such a way as to form peculiar and irregular cavities which open to the outside near the tip of the leaf. There is no doubt that animalcula of sorts get into these cavities and probably die there. In that case, their remains will form a useful supplement to the diet of the plant. The following remarks, however, taken from Kerner have been disputed by other botanists.
Certain of the cells lining these cavities "appear to send out delicate filaments.
"When small animals penetrate into the labyrinthine chambers of a Lathraea leaf and touch the organs just described, the protoplasmic filaments are protruded and lay themselves upon the intruders. They act as prehensile arms in holding the smaller prey, chiefly Infusoria, and impede the motion of larger animals so as to cut off their retreat. No special secretion has been observed to be exuded in the foliar chambers of Lathraea. But seeing that some time after the creatures have entered the chambers, the only remains of them that one meets with are claws, legs, bristles, and little amorphous lumps, their sarcode-flesh and blood having vanished and left no trace, we must suppose that the absorption of nutriment from the dead prey here ensues...."[146]