V. SPIliEROCOCCOIDE.E. 89 



laria, and one of its commoner species (G. multlpavtlta) exhibits every stage 

 between a nearly cylindrical, much branched, bush-like frond and a flattened, 

 laciniated membrane. 



The internal structure of the frond presents as many varieties as the outward 

 form. Most of the membranaceous fronds are composed of polygonal cellules, not 

 longer than their breadth, those of the surface stratum frequently tal)ulated. Some- 

 times the interior cellules are of large size compared to the exterior, and gradually 

 diminish as they approach the surface of the frond, the outer stratum being com- 

 posed of minute dot-like cells : in other cases all are nearly of equal diameter. 

 In several the axial or medullary region is occupied by cylindrical cells joined end 

 to end into filaments, which are either solitary', or more commonly bundled toge- 

 ther or closely compacted into an internal midrib. In others almost the Avhole 

 internal substance of the frond is composed of a plexus of such filaments, but this 

 structure is rare in the Order, and confined to some genera of the southern hemi- 

 sphere. As a general rule, an opaque, inarticulate frond, composed of polygonal, 

 tabulated or roundish cellules, is characteristic of these Algte. 



The colour is of various tints, mostly brilliant ones. Some of the finest and 

 purest carmine, crimson and blood-red hues seen among marine plants, are found 

 in this Order. Others are purple-lake, of greater or less brilliancy ; and a few, 

 chiefly of the filiform kinds, are dull-red, brownish or whitish, tinted with various 

 pale shades of red, or greenish yellow, the latter colours indicating a weak or 

 blanched growth. 



The distinctive character of the Order is found in the structure of the sporiferous- 

 nucleus, whicli consists of a dense tuft of simple or branched, moniliform spore- 

 threads radiating from a cellular placenta fixed in the base of the cavity of an 

 external conceptacle. The conceptacle is of various forms ; bottle-shaped with a 

 prominent orifice, conical, hemispherical or spherical, in the latter cases generally 

 destitute of a pore, and emitting the spores only on the bursting of the pericarp. 

 The walls of this conceptacle are membranous, thick or thin, composed of one or 

 of several strata of cellules. The cavity is generally large, rarely quite filled by 

 the nucleus. The placenta sometimes projects into the cavit}^ so as to fill one-half 

 of the space, and sometimes is but slightly developed. It is always cellular, and 

 generally solid ; sometimes, however, hollowed out beneath. The whole surface is 

 densely covered with vertical or radiating simple or dichotomous spore-threads, 

 each consisting of numerous ellipsoidal or roundish cellules which are gradually 

 converted into spores, the terminal cell ripening earlier than the others. 



The tetraspores are either tripartite or rarely zone-parted, and are either dispersed 

 over the Avhole frond, or more frequently collected into definite groups or sori, 

 which are sometimes borne in proper leaf-like processes of the frond. 1 hey are 

 ahvays sunk among the superficial cells ; never collected in nemathecia, but some- 

 times lodged in thickened wart-like prominences rising from the membrane. 



Many of the genera of this Order are widely dispersed. The Delesserice and Nito- 

 phylla are among the most beautiful of leafy sea-weeds, and are found between 

 the parallels of 30° and 60° north and south of the equator, but are more abundant 

 on the luiropean than the American Atlantic coasts. On the North American 



VOL. IV. — AUT. 5. N 



