Now, that this latter is merely a variety of the broad-leaved clover there can be but little doubt; still the fact that it is usually more perennial in its habit is of importance. We may easily understand why it should be so, if we consider that the common broad-leaved clover in its cultivation is so much earlier than the cow-grass form, so that this enables two cuttings of the former to be made in one season, two crops of hay being taken very commonly indeed; and as the plant gets well in flower before it is cut the first time, and seed is saved from the second crop, a more exhaustive plan for the crop itself or its future perennial powers could hardly be brought about. The cow-grass clover, however, is a fortnight and more later, which renders it difficult to cut two crops; and so its method of growth is not so exhaustive. We know that the common wild clover is said to last only two years, but with constant depasturing we see no reason why the same roots should not send up herbage for five or even ten years. However theoretical such inquiries may be deemed, yet it must be confessed that they are of great practical importance; for, if a plant has a tendency to run into varieties, it makes it daily more difficult to get its seed true to sort; and if we are liable to have a sample, part of which may be less hardy or part more tardy in its development, it follows that much of it may never arrive at maturity, whilst if it does, as the crop will be uneven, it can never be reckoned upon for so good a yield. Much of the variable nature of the sorts which we observe in a clover-field may be the result of the mixing of seeds from different and distant localities: if so, it is much to be regretted. But this only tends to show us how important it is that seed should be grown with care, to which end, as regards clover-seed, we sadly want some well-conducted experiments on different varieties, especially of a wild native plant, with a view to obtain a sample with good, permanent, and even qualities. In fact, the question of true of sort is altogether different from that of purity of sample; but that very serious mischief arises from the want of the latter will be discussed in another chapter. CHAPTER XX. ON THE CLOVER ALLIES. Besides the clovers proper, there are many native plants of the same natural order that have been found useful as fodder: these it is now proposed to comment upon, premising that as we have had them all under cultivation, we are enabled to discuss their merits from a practical point of view. Of these, the following is a list of the genera:— I. ULEX.—A spinous shrub. II. ANTHYLLIS.—Flowers in a dense head, with white expanded calyces. III. LOTUS.—Flowers in lax heads; pod straight, many-seeded. IV. MEDICAGO.—Flowers various; pod spirally twisted. V. MELILOTUS.—Flowers in spikes, drooping to one side; pod straight, few-seeded.