198 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



is not found on our coasts. It occurs at the Cape, and in 

 Australia, under two or three forms. But if such species as 

 Ghyclocladict parvula he rightly included in the genus, we 

 have at least, on our southern coasts, one elegant represent- 

 ative, and an allied form occurs at New Zealand. The fruit 

 of 0. parvula, indeed, is at first sight like that of true 

 Lomentariw, but the placenta consists of a clathroid reticu- 

 lated mass of threads, on which the spores are seated singly"; 

 while in Champia lumbricalis there are short necklaces 

 of spores of a less decided pear-shaped outline. In fact, the 

 differences are greater than exist between many genera. 

 Lomentarm is well represented by the old Fucus Kaliformis, 

 which sometimes grows to a large size, and L. ovalis is a rarer 

 but scarcely less beautiful British seaweed. 



176. In these latter genera the placenta consists not simply 

 of a tuft of threads, but of a clathrate mass, studded with 

 obconic spores. Without great care the nuclei may be mis- 

 taken for favellae, to which they have at first sight a consi- 

 derable resemblance. Cladhymenia and Delisea are Austra- 

 lian. Laurenoia pinnatifida is the Pepper Dulse of Scotland, 

 but certainly not so agreeable an article of food as Alaria 

 escidenta, or the common Dulse. The other equally common 

 species is probably no less wholesome, and siipplies a portion 

 of what is sold in the shops under the name of Helmintho- 

 chorton. Both these species occur on the North American 

 coast, the one on the east, the other on the west ; and there 

 are several other species. 



177. As the antheridia of Laurencia attain a greater 

 degree of complication than in the other tribes, I shall take 

 this opportunity of saying a few words on the subject. I am 

 not aware that any observations have at present been made 

 which confirm theoretic notions, as to the functions of the 

 bodies which they contain. In Callithamnion, JVemalion, 

 Griffiihsia, and Geramium, the antheridia consist of little 

 clusters of cells, variously arranged, in which the spermato- 

 zoids are generated. In Wrangelia, Dasya, and Polysiphonia 

 they assume the form of a pod, which is filled with cells, but 

 not, as before, naked. A near approach to this is made in 



