SECTION III. 
RHODOSPERMESA. 
ted Seaweeds. 
UNTIL so comparatively recent a period as the summer of 1857, the 
standard work on British Marine Algx, both as regards systematic 
arrangement and nomenclature, was Professor Harvey’s ‘ Phycologia 
Britannica,” in which magnificent publication the “ rose-tangles,’”’ or red 
seaweeds, are described under the general title of Rhodospermee, or 
red-seeded plants. But since the completion of Professor Harvey’s great 
work, a new arrangement of the Rhodosperms has been published by 
Professor Agardh, the Swedish algologist. This arrangement is based 
on a more accurately scientific investigation of the sporiferous nuclei, . 
or spore-producing bodies, in the various species of this great subdivision. 
The Agardhian arrangement of the red seaweeds is divided into two 
series, the lesser organised families being included under the title 
Gongylospermee, or plants whose sporiferous nuclei contain numerous 
spores congregated without order in each nucleus or spore receptacle, 
and the more highly organised families classed under the title Desmio- 
spermee, the sporiferous nuclei of these consisting of tufted spore threads 
or filaments, a single spore being formed in each cell of the tufted threads, 
or only in the terminal cell. Some portions even of this arrangement 
have been modified or altered, and the names of many species have been 
changed by Professor Agardh himself, and as I am convinced that all 
these recent changes have been the result of the most definite and accurate 
observation, it is my intention in describing the British Rhodosperms, to 
adopt Professor Agardh’s arrangement, and most recent nomenclature ; 
although, for my own convenience, particularly as regards the extreme 
difficulty of preparing many of the illustrations, I shall now and then be 
compelled to describe families, or at least genera, somewhat out of regular 
scientific order. However, to the general reader, and even to young 
algological students, this will make no difference whatever as to their 
acquisition of a knowledge of the plants themselves, which is indeed, after 
all, my primary object in writing this work. 
Although, to ordinary observation, the most striking characteristic of 
the plants of this great subdivision is their colour, the scientific student 
finds a more remarkable and distinctive characteristic in the double 
system of fructification, nearly every genus being furnished with two 
different kinds of reproductive bodies, or spore-bearing organs, which are 
