And this earlier stem,--what of it? It too had been a shoot, a pair of cotyledons with a plumule, a seed, an integral part of a carpel, which was a part of an earlier flower, that expanded from an earlier bud, that grew out of an earlier stem, that had been a still earlier seed, that had been--and backward, _ad infinitum_, for aught that I can perceive. The course, then, of a scarlet runner is a circle, without beginning or end:--that is, I mean, without a natural, a normal beginning or end. For at what point of its history can you put your finger, and say, "Here is the commencement of this organism, before which there is a blank; here it began to exist?" There is no such point; no stage which does not look back to a previous stage, on which _this_ stage is inevitably and absolutely dependent. To some of my readers this may be rendered more clear by the accompanying diagram:---- [Illustration: legume--reed--cotyledons--shoot--stem--bud--flower--carpel] [Illustration: theca--spore--prothallus--sporal frond--tuft--caudex--fertile frond--sorus] See that magnificent tuft of Lady-fern on yonder bank, arching its exquisitely cut fronds so elegantly on every side. A few years ago this ample crown was but a single small frond, which you would probably not have recognised as that of a Lady-fern. Somewhat earlier than this, the plant was a minute flat green expansion (_prothallus_), of no definite outline, very much like a Liverwort. This had been previously a three-sided spore lying on the damp earth, whither it had been jerked by the rupture of a capsule (_theca_). For this spore, though so small as to be visible only by microscopic aid, had a previous history, which may be traced without difficulty. It was generated with hundreds more, in one of many capsules, which, were crowded together, beneath the oval bit of membrane, that covered one of the brown spots (_sori_), which were developed in the under surface of the fronds of an earlier Lady-fern. That earlier individual had in turn passed through the same stages of sporal frond, prothallus, spore, theca, sorus, frond, prothallus, spore, theca, sorus, frond, prothallus, &c.--_ad infinitum_.