. British marine algae : being a popular account of the seaweeds of Great Britain, their collection and preservation. Marine algae. INTRODUCTION. plant from being driven about and destroyed by the action of the waves ; but as no vessels of absorption have hitherto been discovered in the roots and stems, it is evident that seaweeds do not derive their nourishment from the substance to which they are attached, for indeed they are found growing luxuriantly alike on iron and floating timber, on rocks and shells, on the carapaces of crabs, and even upon each other, in the latter case without any de
. British marine algae : being a popular account of the seaweeds of Great Britain, their collection and preservation. Marine algae. INTRODUCTION. plant from being driven about and destroyed by the action of the waves ; but as no vessels of absorption have hitherto been discovered in the roots and stems, it is evident that seaweeds do not derive their nourishment from the substance to which they are attached, for indeed they are found growing luxuriantly alike on iron and floating timber, on rocks and shells, on the carapaces of crabs, and even upon each other, in the latter case without any detriment whatever to the species on which they are parasitic. The roots or holdfasts in some are a flattened or slightly conical disc, in others branching and clinging fibres, and in the Laminarice or oarweeds, especially as the plants advance in growth, a series of grasping processes are thrown down from the stem, which adhere so firmly to the rock that it is extremely difficult to detach them. The algse, or seaweeds, consist entirely of cellular tissue—little mem- branous sacs or cells of various forms, with walls of different degrees of tenacity. These minute cells are empty or filled with granular organised matter, which divides and developes new cells; these again divide and produce others, and thus by this cell splitting, branches and spreading fronds or leafy expansions are produced, each order of cell-division proceeding according to the laws of growth of its own species. The cellular tissue of which all seaweeds are composed presents several varieties. The most common form of cell is that of a cylinder, generally much longer in propor- tion to its breadth, and when such is the case the cells are attached end to end, forming threads or filaments, numbers of which, branched or otherwise, make up the frond by becoming firmly attached in bundles. Many of the simpler kinds of seaweeds are made up of threads or strings of cells, some of which are elaborately branched, other
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