Having thus taken a view of the Organical Parts of the Bean, let us next examine the Similary, sc. those whereof the Organical are compos’d: a distinct observation of which, for a clear understanding of the Vegetation of the Seed, and of the whole Plant arising thence, is requisite: To obtain which, we must proceed in our Anatomy.
Dissecting a Bean then, the first Part occurring is its Cuticle. The Eye and first Thoughts suggest it to be only a more dense and glossy Superficies; but better enquiry discovers it a real Cuticle. ’Tis so exquisitely thin, and for the most part so firmly continuous with the Body of the Bean, that it cannot, except in some small Rag, be distinctly seen; which, by carrying your Knife superficially into the Bean, and then very gently bearing upward what you have cut, will separate and shew it self transparent. This Cuticle is not only spread upon the Convex of the Lobes, but also on their Flats, where they are contiguous, extending it self likewise upon both the Radicle and Plume, and so over the whole Bean.
This Part, though it be so far common with the Coats of the Bean, as to be like those, an Integument; yet are we in a quite different Notion to conceive of it: For whereas the Coats upon setting the Bean, do only administer the Sap, and, as being superseded from their Office, then die; as shall be seen: this, on the contrary, with the Organical Parts of the Bean, is nourished, augmented, and by a real Vegetation co-extended.
Next to the Cuticle, we come to the Parenchyma it self; the Part throughout which the inner Body, whereof we shall speak anon, is disseminated; for which reason I call it the Parenchyma. The Surface hereof is somewhat dense, but inwardly ’tis more porous, and of a laxer Contexture. If you view it in a Microscope, it hath some similitude to the Pith, while sappy, in the Roots and Trunks of Plants; and that for good reason, as in [Ch. 2.] shall be seen. This is best seen in green Beans. [See Fig. 2.]
This Part would seem by its colour to be peculiar to the Lobes of the Bean; but as is the Cuticle, so is this also, common both to the Radicle and Plume; that is, the Parenchyma of the Bean, as to its essential substance, is the same in all three. The reason why the colour of the Plume, and especially of the Radicle, which is white, is so different from that of the Lobes, may chiefly depend upon their being more compact and dense, and thence their different Tinctures. And therefore the Lobes themselves, which are green while the Bean is young; yet being old and dry, become whitish too. And in many other Seeds, as Acorns, Almonds, the Kernels of Apples, Plums, Nuts, &c. the Lobes, even fresh and young, are pure white as the Radicle it self.
But although the Parenchyma be common, as is said, to all the Organical Parts; yet in very differing proportions. In the Plume, where it is proportionably least, it maketh about three Fifths of the whole Plume; in the Radicle, it maketh about five Seavenths of the whole Radicle; and in each Lobe, is so far over-proportionate, as to make at least nine Tenths of the whole Lobe.
By what hath been said, that the Parenchyma is not the only constituting Part, besides the Cuticle, is imply’d: there being another Body, of an essentially different substance, embosom’d herein: which may be found, not only in the Radicle and Plume, but also in the Lobes themselves, and so in the whole Bean. [See Fig. 2.]
This inner Body appears most plain and conspicuous in cutting the Radicle athwart, and so proceeding by degrees towards the Plume, through both which it runneth in a large and straight Trunk. In the Lobes, being it is there in so very small proportion, ’tis difficultly seen, especially towards their Verges: yet if with a sharp Knife you smoothly cut the Lobes of the Bean athwart, divers small Specks, of a different colour from that of the Parenchyma, standing therein all along in a Line, may be observ’d; which Specks are the Terminations of the Branches of this inner Body. [See Fig. 3.]
For this inner Body, as it is existent in every Organical part of the Bean, so is it, with respect to each part, most regularly distributed. In a good part of the Radicle ’tis one entire Trunk; towards the Basis thereof, ’tis divided into three main Branches; the middlemost runneth directly into the Plume; the other two on either side it, after a little space, pass into the Lobes; where the said Branches dividing themselves into other smaller; and those into more, and smaller again, are terminated towards the Verges of each Lobe; in which manner the said inner Body being distributed, it becomes in each Lobe, a true and perfect Root. [See Fig. 2.]
This Seminal Root, as now we’ll call it, being so tender, cannot be perfectly excarnated, as may the Vessels in the Parts of an Animal, by the most accurate Hand; yet by dissection begun and continu’d, as is above-declared, its whole frame and distribution may be easily observ’d. Again, if you take the Lobe of a Bean, and lengthwise pare off its Parenchyma by degrees, and in very thin Shives, many Branches of the Seminal Root, (which by the other way of Dissection were only noted by so many Specks) both as they are fewer about the Basis of the Bean, and more numerous towards its Verges, in some good distinction and entireness will appear. For this you must have new Beans.