If, however, there should be any doubt about pure sainfoin seed, we should recommend the decorticated seed being used, as in it the burnet could not possibly escape detection.
As the history of burnet is so important in connection with the sainfoin crop, it cannot be out of place to introduce the following description of this weed:—
The Sanguisorba officinalis (false burnet), as a wild plant, never attains any great size, and as it is a denizen of dry calcareous pastures and broken ground on limestones, and perfectly harmless in its properties in this condition, it is scarcely noticeable as a weed; indeed, it is sometimes recommended for permanent pasture admixture on calcareous uplands. There is, however, a larger form of the false burnet, which is now attracting considerable attention, as being by far too constant an attendant upon sainfoin seed.
This plant is referred by Professor Babington and the Continental botanists to another species, viz., Poterium muricatum, which is by them distinguished from the P. sanguisorba; but is “usually larger in all its parts” (Bab.), with a larger and more decidedly four-winged fruit. We, however, agree with Bentham in considering this to be a variety only, and, in fact, an agrarian form, induced by its seed being gathered with a crop and treated as a crop plant, so that its larger form may be easily accounted for; and we are not wanting in evidence to show that, under cultivation, the P. sanguisorba greatly increases in size, while, if left to grow wild, the cultivated form relapses into the wilder state. But we incline to think that the agrarian burnet has got into agriculture by being introduced with foreign seeds; and as its introduction seems to have been small at first, it attracted but little notice; for as the leaves both of the burnet and sainfoin were pinnate, the difference that the botanist would observe in the leaflets, i.e. the former being serrate, and those of the latter having an entire margin, would hardly attract the attention of the farmer; however, it soon became so serious a matter that some crops of so-called sainfoin, in their second or third year, presented as much as 90 per cent. of burnet, and as the latter grew taller than the sainfoin, it effectually smothered it out, and in its place supplied a sticky, non-succulent, and innutritious herbage, that made farmers begin to inquire seriously about the seed.
Here, however, as the seeds, or rather the fruits, of both plants were pretty much of the same colour, and both wrinkled, samples of fully half burnet passed muster in the seed-market; and, though these fruits are so different in shape and size, yet we were astonished to find that, during the trial of an action against a seedsman for supplying sainfoin seed containing a large quantity of burnet when good sainfoin seed was paid for, the judge, jury, and most of the farmers present confessed their inability to distinguish them; it becomes, therefore, at this point, a duty to describe the two.
Fig. 32.
[Fig. 32 a] represents a short wrinkled pea-pod, broad at the back and thin in front, as seen in the section [b]. In the interior is a single pulse-seed, which is easily freed from its wrinkled shell.