in unfavourable seasons, when such bees are scarce, much clover fails to produce seed.

When it was first introduced into our Colonies in the Southern Hemisphere, complaints arose of its failure, so the English humble-bee was imported. This was said to overcome the difficulty. But it appears to have failed only in some places; for in others reports were received that there was no difficulty in getting seed, but whether by native bees or by acquired selffertilization was not stated.

It may be mentioned that it was thought at one time that selffertilization was injurious, and that plants habitually setting seed by their own pollen grew weaker and weaker, and finally died out. This was due to an error of observation. They are mostly insignificant flowers; but for health, vigour, and abundance of good seed, the plants are not to be surpassed. Moreover, self-fertilizing "weeds" are far more widely dispersed over the globe than the plants which display brighter and larger flowers, but are dependent upon the capricious visits of insects for fertilization.

Mr. Darwin made a large number of experiments in "crossing" some and "self-fertilizing" others, artificially, of the same kinds of plants. He then compared

the offspring in all sorts of ways, as to heights and fertility. He generally found that with the first two or three generations the "crossed" plant beat the "self-fertilized."

But he rarely continued the experiments for a sufficient number of years. For crossing is a temporary stimulus; and after a few years the continually selffertilized gradually gain upon the intercrossed, and then far outstrip them in fertility.

Florists corroborate this result. By constantly crossing to procure finer flowers, after a time fertility rapidly decreases, and it is often next to impossible to get the finest flowers to set any seed at all. Just as pigeon-fanciers say the best pigeons always die in the nest, so a certain florist lost his whole stock of valuable primulas from this cause.

On the other hand, self-fertilizing weeds as Groundshell, Shepherd's-purse, Black Solanum, Chickweed, etc., are sturdy little plants, terribly prolific, and an intolerable nuisance in the garden.

THE STEMS AND FOLIAGE OF PLANTS

CHARACTERISTIC OF DRY REGIONS.

As we are going to study plants of a region characterized by great drought, we will now pay a little attention to the general features of the vegetative organs of the natives of such a country, as their special adaptations to a dry soil and air, and a paucity of water during the summer, are very pronounced both in the stems and leaves of many plants.

After the rainy season, plants which maintain a show of foliage only during the period of seasonal rains, and dry off with the advance of drought, exhibit quite a different sort of leaves from those borne by plants which persist all the year round, and therefore have to withstand a long period of drought. Take the many species of Ox'alis. They have thin and bright green leaves; but think of the shrubs in January. They bear leaves almost leathery in character, such, for example, as the Sugar-bush and Wagen-boom. Their toughness is due to the thick skins they have, which prevent water escaping too quickly in the dry summer.

Plants growing in dry places, which cannot get enough water, are often unable to make full-sized leaves. The result is that while the "mid-rib" and the side ones are developed, the pieces of the leaf which ought to fill up the interspaces are not formed, so that the whole leaf may be deeply cut down in appearance. There is a common shrub used for hedges about Cape Town and elsewhere, the leaves of which are like a double comb. It is called Ha'kea, and came from Australia. It is a member of the same family as the Sugar-bush.

One general result of a dry climate is to reduce the size of the leaves greatly. Hence so many plants in the Colony look like heaths, of which there are some 500 different kinds; but as one goes eastwards to Port Elizabeth and beyond, the climate is moister, and they are much less numerous, partly from this, as well as other causes, till they cease to occur altogether.

The next thing to notice is, how often leaves are hairy. Thus those of the silver tree are densely clothed with silky hairs. In many cases the hair makes a coating of wool, as on some of the Everlastings. The use of hair is to reduce the heat from sun, to lessen the loss of water, and also to absorb dew for the benefit of the plant when the rain or dew falls.

Another result of drought is the hardening of the woody parts so that the tips of leaves are often sharp pointed; and the shoots also are checked in their growth,

and end in sharp spines, as in the Kei-apple tree, and of the tree shown on Fig. 19.

But besides this hardening effect of drought and heat, many plants have adopted a plan of storing up the water when the rain falls. Thus the very common plants known as Mesembrian'themum have thick, fleshy

leaves, full of water, and protected by a thick skin; one species, called the "Ice-plant," is covered with little bladder-like projections on the leaves, each of which is like a miniature bottle of water without a neck, Many of the Cras'sula family are similarly provided; while others, as the fleshy Euphorbias and Stapelias, store up water in their stems (Fig. 20). Hence all