Dr II a/del:berg's Method.
Dr 'sVahlenberg proposes the division of the Linnesn genus Focus into three genera, or rather tribes : Fucus, properly so called ; Spizcerococcon ; and Palmaria.
1. Fucus: " Semina in capsulis poro dehiscentibus, ag gregatis, frondi simulque aclsunt vesiculvesicularsim plices seu articulatx. This includes F. setratus, vesicu losus, siliquosus, nodosus, loreus.
2. Slzh cerococcon ; " Semina in capsulis imperforatis, so litariis, superficialibus; simulque adsunt granula immersa in appendicibus foliorum, fere ut in confervis." This takes in F. sanguineus, alatus, plumosus.
3. Palmaria : " Semina solitaria nuda, in frondium su perficie." This includes the large fuci, as F. digitritus, and saccharinus, (Turn. t. 163.) He adopts the following subdivisions : (1.) Frondescent, with a simple midrib or nerve in the centre of the frond ; as F. serratus and vesiculosus.
(2.) Frondescent, with branched veins or nerves ; as F. sanguineus, and sinuosus, (Turn. t. 55.) (3.) Stipitate, with a simple stern, proceeding from a fingered root, and spreading out into a broad frond ; as F. digitatus and saccharinus.
(4.) Foliaceous and stemless, membranaceous, without nerves or veins; as F. palmalus, and canaliculalus (Turn.
t. 3 ) (5.) Caulescent, with distinct fruit-bearing processes, (i. e. receptacles), which are deciduous; as F. siliquosus and nodosus.
(6.) Caulescent, naked and compressed ; as F. 'omits and plumosus.
(7.) Filiform, with spherical fronds ; as F. filum and ly copodiodes.
311. Lamouroux's Method.
Lamouroux, far from confining himself to the fructifica tion as the basis of his divisions, derives his characters from every part of the plant, or even from any remarkable accessary circumstance. He divides all the thalassiophytes into six Orders, viz. Fucacex, Flotidex, Dietyoteze, Ul vacex, Aleyonideoz, and Spongodex.
The first order, FUCACE/E, is the most numerous. They are distinguished by their " woody structure, and their co lour being somewhat olive, drying to blackish."
iNlost of the species of this family have distinct sterns and leaves. In the stems of the larger kinds, particularly in F. digitatus, may he observed parts analogous to the epider mis, bark, wood, and pith of land plants. The Fucacex are readily torn in a longitudinal direction, and a well cha racterized fibrous organization is then displayed. In ral the fibres are divided by septa ; the partitions being more distant and of a looser texture than in herbaceous plants. In most of the Fticace:e the organs of fructifica tion are complicated : According to Lamouroux, the seeds are inclosed in capsules ; these capsules are themseles en veloped by a particular membrane, and form tubercles ; and these tubercles are grouped into polymorphous masses. These masses are attached to the branches or to the extre mities of fronds ; they contain a mucilaginous matter, the quantity and viscidity of which increase as the seeds ripen ; and when they are dispersed, it disappears with them. The fronds of the Fucacex vary in composition, situation, gene ral or particular shape, with or without nerves ; exhibiting a variety almost as great as the leaves of dicotyledonous plants.
The 1st genus is Fucus, which is thus defined : " Tuber cles numerous, collected in cylindrical receptacles, which are flat or compressed, solitary or in pairs ; the root an ex panding callous disk." This character has no doubt the effect greatly to reduce the numbers of the old genus Fu cus ; but it is still very extensive, and the author has judged it necessary to divide it into no fewer than eleven sections. Plants which materially di er in general aspect and habit are still brought together . s F. natans, siliquosus, vesi culosus, loreus, and canaliculatus, are arranged under this one genus ; while we might expect them to form as many distinct genera. In specifying the different sections, some of the best known or most remarkable species shall mentioned as examples.