By attending to the characters in Lamouroux's arrange ment, a general idea may be gathered of the families of foci in which the different kinds of fructification occur, whether consisting of receptacles, tubercles, capsules, or patches. It seems unnecessary, therefore, to enlarge much on this subject. A few farther remarks on the double mode of fructincation, may however be proper. This double mode, it will he remembered, occurs either on the same plant, or on separate individuals of the same species ; and it is of various kinds, some of which may be mentioned.
a. On different individuals of the same species, globular capsules and lanceolate capsules are observed, as in F. sub fuscus, status, pinastroides (Turn. t. 11.), and coccincus (see Plate CCLXI. Fig. 10, 11.) and both these kinds of capsOlcs sometimes occur on the same frond of the last named species. This fact did not escape Mr Stackhouse; for in his Xereis Britannica, he makes it part of the specific character of F. coccineus, that it bears polymorphous fruc tification ; and Mr Turner, in his Synopsis, afterwards di vided it into two varieties, one with spherical capsules, the other with lanceolate or elliptical capsules.
b. On the same individual, lineari-lanceolate capsules, and also pedunculate capsules of an orecolate form, as in F. dentatus. (Plate CCXLI. Fig. 8, 9.) c. Lanceolate capsules and small patches of naked seeds are found on the same plant ; as in F. hypoglossum, (Turn. t. 14.) d. Ovate capsules and spherical immersed seeds, on the same individual ; as in F. dasyphyllus, (Turn. t. 22.) e. Ovate and oblong capsules, on the same plant ; as in F. acanthophorus of Lamonroux, (Turn. t. 32.) f. Cilia containing seeds, on the margins and midrib of • the plant ; and spherical tubercles immersed in obovate processes on different parts of the plant ; as in F. sinuosus. (Plate CCLXI. Fig. 6, 7.) g. Urceolate sessile capsules on one plant, and naked seeds immersed in the frond on another plant of the same species ; as in F. articulates. It is a remark of M. Lamou roux, that the double fructification is never found on the truly articulated sea-weeds, that is, the marine conferm : but in this he seems mistaken, as the double mode occurs in the plant named Focus fruticulosus, (Turn. t. 227), which, as Mr Turner properly remarks, belongs to the con fervx.
In a few capsuliferous species, as F. plumosus and flac cidus, (Turn. t. 61), the seeds, or what are reckoned the seeds, are not inclosed in proper capsules, but merely sur rounded by seue, producing the appetutance of an involu crum. In the large species, F. sacebarinus and bulbosus, the fructification is in irregular patches on the frond, and consists of a profusion of seeds imbedded among whitish fibres, but without any covering or epidermis. Mr Bro die of Brodie, in a communication to Mr Turner, (Hist. Fuc. vol. iii. p. 62.) very aptly compares a section of the last-named species when in fruit, and placed under the mi croscope, to a section of a syngenesious flower, with the seeds protruding from the receptacle among the bristly pappus.
It has already been stated, that in some species there are found both seeds in tubercles, and seeds scattered in the substance of the frond. Mr Turner was at one time of opinion, that the seeds in the tubercles might become sub sequently disseminated through the frond ; but more care fitl examination with the microscope, enabled him to satisfy himself that the capsular granules differ as to shape from those which lie naked in the frond.
He is inclined to believe, that those plants on which the two modes of fructification occur on different individuals, are truly direcious, though a plant, possessing each mode of fructification, may frequently arise from the same basis, and thus occasion ambiguity. Dr Solander, it may be re marked, first suggested that these might he male and fe male. It would evidently be almost a hopeless attempt, to endeavour to observe the mode of impregnation in their native element ; and it is not improbable that this may for ever remain among the arcana of nature.
A few species have a proliferous tendency, putting forth peltate leaves, ready to lengthen into branches, if the plant have sufficient vigour. Mr Turner seems to think it pro bable, that, like the bulbs of allia, these new productions may fall off when the frond decays, and shoot up into inde pendent individuals. Some species, that have broad ter minal receptacles, have been observed occasionally to be come viviparous, particularly F. vesiculosus and serratus ; the seeds vegetating while in the receptacles, and thus pro ducing the viviparous character.