RHODOSPERME.E. 69 



one of the principal characteristics of the sub-class. But 

 there is no reason why similar regularity should not accom- 

 pany the formation of gemmules, if this latter be one of the 

 modes of propagation which Nature has specially assigned 

 to these vegetables. 



The second kind of fruit the simple spore (or gemmule 

 of J. Agardh) is a much less organized body than the tetra- 

 spore, and more irregular in form ; but it is superior, for the 

 most part, in the position it occupies. That is to say, sim- 

 ple spores are never, like tetraspores, dispersed through the 

 tissue of the frond, but are always grouped together in defi- 

 nite masses, which very generally are enclosed in a more or 

 less perfectly formed pericarp or conceptacle. They have 

 therefore, to the unassisted eye, much more the appearance 

 of fructification than tetraspores have, unless where the latter 

 are placed in stichidia. In the simplest form of conceptacu- 

 lar fruit, such as we find in Halymenia and Dumontia, 

 there is no proper conceptacle, but the spores are collected 

 in spherical masses, and either attached to the wall of the 

 frond or imbedded in its substance, in which case, the tissue 

 surrounding the mass of spores is destitute of colouring mat- 

 ter. Such a fructification is called a favellidium ; and the 

 name is commonly extended to fruits of a similar structure, 

 but which are not perfectly immersed, such as we find in 

 Gigartina, Gelidium, &c., where they exist as tubercular 

 swellings of the branches. In some cases these swellings 

 communicate at maturity with the surface by a pore, through 

 which the spores find exit. When such a fructification is 

 wholly external, as in Callithamnion and Ceramium, it is 

 called a favella. Nearly related to this, and especially to 

 the semi-external favellidia of Gigartina, &c., is the fruit 

 called coccidium, the characteristic conceptacle of Rhody- 

 menia, Delesseria, Nitophyllum, &c. This may either be 

 borne on lateral branches, or sessile on the surface of the 

 frond. It consists of a hollow case, with thick, cellular 

 w r alls, containing a dense tuft of angular spores attached to a 

 central placenta. Most generally it is impervious, but occa- 

 sionally pierced by a pore, through which the spores are 

 discharged. Lastly, in the ceramidium the conceptacular 

 fruit is brought to its highest development. This organ is 

 ovate or urn-shaped, furnished with an apical pore, and con- 

 taining a tuft of pear-shaped spores, rising from the base of 

 the cavity. The walls are usually thin and membranous, 

 and the hollow space considerable. Such is the conceptacle 

 of Polysiphonia, Dasya, Laurencia, &c. These are the 



