A LEXANDRITE, a name given to specimens of the mineral Cliry soberyt, brought from the Ural. [Cnevsonsevt.] A LasE Is the name given by botanists to the tribe of plants which comprehends the Sea-Weetle, Lavers, and fresh-water nubmersed species of similar habits'. In structure they vary through a vast variety of intermediate gradations, from the state of simple microscopic vesicles to branched woody individuals many fathoms in length. Some of them are only visible to the naked eye when they are collected in heaps; of this nature is the green and red slime that we find in damp walks, at the bottom of shaded walls, and in similar situations ; others grow together in the beds of the ocean, and when they rise to the surface form floating banks of such extent as to impede the course of ships ; of this kind are the Chorda filam, or Si* Cat.-Out, of Orkney, meadows of which have been seen in Seal's Bay ; and the Gulf.Weed of navigators, which, according to 11 being (lurked by the Gulf Stream, forms two bunks in the great banns of the Northern Atlantic Ocean, one of which stretches over 11 degrees of latitude, and the other over 4 degrees.
The plants included under this designation are every day becoming better known through the influence which the microscope and better methods of investigation are producing in every department of natural history. Under the term Aire- Linnaeus included the Lichens and other plants as an order in the class Cryptogetnia, or Aeroyens. The Lichens have been long since separated ; but tho 'Untie that are now ordinarily called Aissfr present differences quite as wide as any that separate the orders of the class Erourns, so that we cannot regard the term Alfpr us of only ordinal value. Dr. Lindley, in his ' Vegetable Kingdom, constitutes an alliance which he calls A ludo, and which he makes to embrace the following natural orders s 1. Diatomeecer, or Brittleworts.
2. Conferrecar, or Confervive 3. Fecacar, or Sea Wracks.
4. Cererniacetr, or Hose Tangle& 5. Character, or Charade The first of these orders includes the Desmaerr, which are almost entirely microscopic. They are hardly comprehended under the
term Aloe at all. [Dissosscesa ; Dessueess] It is only very recently that naturalists have come to the conclusion that they are plants. The Charade, or fifth order, present in many respects a much higher development than the rest, and may be justly regarded SS not belonging to Alga.. [Cleanses:x..] The relation of these groups to each other end the animal kingdom may be seen in tho following diagram, given by Professor Harvey in his work on the 'British Algie.
An Mr. Harvey is the most recent writer on this subject we shall follow him in this article. He divides the Algte into three sub-clnaecs.
1. 3Ielanosperrnem, which are marine plants of nil olive green, or olive brown colour, having a monsecious or dirocious fructification. The spores are olive-coloured ; each enveloped in n pellucid skin, and either simple, or separating into two, four, or eight sporulec. They possess antheridia, or transparent, orange-coloured, vivacious corpuscles, moving by means of vibratile cilia.
2. Rhodospermeas which, with one or two exceptions, are marine plants, mostly of a rosy red or purple colour. The fructification u of two kinds : either of spores in external or immersed conceptaclers or densely aggregated together and dispersed throughout masses of the frond ; or of tetrnapores of a red or purple colour, external, or immersed in the frond, and each enveloped in a pellucid skin which nt maturity separates into four sporules. Some possess autheridia which are filled with yellow corpuscles.
3. Chlorospermetr, which are marine or (midi-water plants cf a green colour. The fructification is dispersed through all parts of tho frond. The spores are green, formed within the cells, and often at maturity having vibratile cilia. They produce also genunnlen, or extirnal vesicles, which contain a demo, dark-coloured, granular mass, which finally separated from the frond.