The higher tribes of Algæ embrace the sea-weeds; these are for the most part broad, leaf-like expansions of "thallus," composed of cellular tissue, they sometimes grow to an enormous length. Humboldt mentions the sea-grass as extending for miles, and forming continuous extensions of two or three hundred feet, and the _Macrocystis pyrifera_ attains to the length of more than a thousand. The common Bladder-wrack (_Fucus vesiculosus_) was formerly much used to procure soda from, its ashes containing a considerable quantity, it is also used for manure; the _Laminaria digitata_ is eaten under the name of "tangle," and a nutritious jelly is made from the "Carigeen moss" (_Chondrus crispus_). 2. CHARACEÆ (Charas). These are a kind of fresh-water Algæ, composed of tubes of cellular tissue; they are peculiar, from the fact that the spores of the plant have cilia, giving to them the powers of motion and enabling them to swim away and spread the plant afar off. It is in the Charas that the peculiar circulation of the granules of "endochrome" called "cyclosis" is best seen. [Illustration: Charas.] 3. FUNGI (Fungals), including Mushrooms, &c. [Illustration: Eatable Mushroom (Agaricus campestris).] The Fungi comprise a great variety of vegetable growths, from the mould which grows on any animal or vegetable substance, to the mushroom. Some of the moulds or mildews found on various decaying substances are peculiar to them, and in many cases exceedingly destructive. The microscopic fungus _Puccinea graminis_, is the parasite which fixes itself to corn and produces the disease known as mildew, and the _Uredo segetum_ (another microscopic fungus) causes the "smut;" the "bunt" is caused by the _Uredo foetida_, and the "spur," or "ergot," which attacks rye, is caused by the _Acinula clavis_. These fungi completely destroy the grain of corn, in which they form, and propagate in the most rapid manner; the ergot is moreover a dangerous poison to those who eat the bread made of rye infected by it. The Truffle (_Tuber cibarium_) is a kind of underground fungus, and is esteemed a dainty. Mushrooms are also fungi, and several species are sufficiently wholesome; these are the Field Mushroom (_Agaricus campestris_) and the Fairy-ring Mushroom (_Agaricus pratensis_). 4. LICHENES (Lichens), Are those dry scaly growths forming grey, green, or yellow spots on the barks of trees and in various other places, and they grow in a sort of leaf or scale called a "thallus." They are used as articles of food and as "dye-stuffs;" the _Cetraria Icelandica_ is the "Iceland Moss" used here for making a sort of nutritious drink or jelly, the natives of Iceland, however, use it as common food; the _Cladonia rangifarina_, or Reindeer Moss, is the chief food of that useful creature which forms the whole property of the Laplander; and the _Roccella tinctoria_ is the substance from which the dye called "archil" is procured.