This singular alga resembles a tuber and cannot be mistaken for any other plant. Its fronds are gelatinous, fleshy balls, one half of an inch to two inches in diameter, at first solid, afterward lobed and hollow. It grows singly or in bunches on algæ and on sand-covered rocks, and is found in summer on every coast. The common species is known as /L. difformis/ or /L. tuberiformis/. GENUS ^Myrionema^ Minute algæ which grow on other plants and which appear like dark spots, or, at first, like stains, on /Ulva/, /Enteromorpha/, and small red algæ. These spots, which to the naked eye appear like decay, show, under the microscope, a jelly-like substance full of beaded filaments. ORDER =LAMINARIACEÆ= The plants of this order have large and coarse fronds (some attaining an immense size), with stems, branching root-like holdfasts, and expanded leaf-like laminæ. They are leather-like, not articulated, olive-green or brown in color, and sometimes yellow and semi-transparent. They grow in deep water and are found washed ashore. Sometimes small plants are found in deep tide-pools at low-water mark. Some species are perennial. In these instances the stems only survive, and the laminæ are reproduced annually. The new growth takes place at the apex of the stem. The old lamina is pushed off, but is held on the summit of the new growth until the latter has matured. [Illustration: PLATE XI. Dictyosiphon fœniculaceus. Chordaria flagelliformis. Mesoglœa virescens. Mesoglœa divaricata.] [Illustration: PLATE XII. Chorda filum. Agarum Turneri. Alaria esculenta. Laminaria saccharina.] In the genus /Chorda/ the fronds are cylindrical; in /Agarum/ [pg069] the laminæ are perforated; in /Alaria/ there are wing-like leaflets below the laminæ. The /Laminariaceæ/ and /Fucaceæ/ are the seaweeds used in making kelp. For this the algæ are burned, and the ash is then separated into its different mineral constituents and used for various manufacturing purposes. GENUS ^Chorda^ ^C. filum.^ Entire frond cylindrical, divided internally by transverse septa; one fourth to one half of an inch in diameter, tapering at each end; ordinarily one to twelve feet long, but sometimes attaining a length of forty feet. When young the frond is covered with fine, transparent hairs; later it is brown and leather-like. The growth takes place at the base, just above the disk-like holdfast, and at the apex it is constantly dying off. The species is common on Northern shores, at and below low-water mark. Often it is in masses which seem like meadows of waving grass under water. Various small algæ and many zoöphytes are to be found on the fronds. (Plate XII.) GENUS ^Alaria^ This genus is readily distinguishable by the fact that it has leaflets below the lamina. It is found north of Cape Cod.