It does not appear that any other species of Sargassum is originally destitute of roots, even those most closely allied to Sargassum bacciferum, though some of them are not infrequently found both in the fixed, and in considerable masses in the floating state, retaining vitality, and probably propagating themselves in the same manner. Professor Hervey conjectured that the Gulf-weed might be a pelagic variety of Sargassum vulgare, in the same way as the variety subcostatus of Fucus vesiculosus has never been found attached, growing in salt marshes. In the Mediterranean vast quantities of Fucus vesiculosus occur under a peculiar form, consisting entirely of specimens derived from sea-born weed, carried in by the current which sets in to that sea from the Atlantic. GLOSSARY OF BOTANICAL TERMS A ABBREVIATE (_abbreviare_, to shorten), used to indicate that one part is shorter than another. ABERRANT, deviating from the natural form. ABORTION, suppression of an organ, depending on non-development. ABRADED, rubbed off. ABRUPT, ending in an abrupt manner, as the truncated leaf of the tulip-tree; _abruptly pinnate_, ending in two pinnæ--in other words, paripinnate; _abruptly acuminate_, a leaf with a broad extremity, from which a point arises. ACAULESCENT, without an evident stem. ACCESSORY, an addition to a usual number. ACCRESCENT, when parts continue to grow and increase after flowering, as the calyx of _Physalis_ and the styles of _Anemone pulsatilla_. ACCRETION, growing of one part to another. ACCUMBENT, applied to the embryo of _Cruciferæ_ when the cotyledons have their edges applied to the folded radicle. ACEROSE, needle-like, narrow and slender, with a sharp point. ACHÆNE, or ACHÆNIUM, a monospermous seed-vessel which does not open, but the pericarp of which is separable from the seed. ACHLAMYDEOUS, having no floral envelope. ACHROMATIC, applied to lenses which prevent chromatic aberration, _i. e._, show objects without any prismatic colors. ACICULAR, like a needle in form. ACICULUS, a strong bristle. ACINACIFORM, shaped like a sabre or cimeter. ACOTYLEDONOUS, having no cotyledons. ACROCARPI, mosses having their fructification terminating the axis. ACROGENOUS, having a stem increasing by its summit. ACULEATE, furnished with prickles. ACULEUS, a prickle, a process of the bark, not of the wood, as in the rose. ACUMINATE, drawn out into a long point. ACUTE, terminating in a sharp point. ADHERENT, adhesion of parts that are normally separate, as when the calyx is united to the ovary. ADNATE, when an organ is united to another throughout its whole length; as the stipules to the petiole in roses, and the filament and anther in _Ranunculus_. ADPRESSED, or APPRESSED, closely applied to a surface. ADULT, full grown. ADVENTITIOUS, organs produced in abnormal positions, as roots arising from aerial stems.