192 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



propose the division, but we are indebted to Dr. Montagne for 

 almost the only illustrations we possess of the peculiar struc- 

 ture* of the conceptacular fruit. The tetrasporic fruit of 

 ApoiMcea is figured in the Flora of New Zealand, and may- 

 be compared with that of Ctenodus. 



10. Gelidiace^, J. Ag. 



Inarticulate, cartilaginous ; axis com^DOsed of confervoid 

 threads ; conceptacles semi-immersed. Spores attached to a 

 network of threads, or to a fibro-cellular placenta, which either 

 adheres to one wall of the cavity, or runs through its centre, 

 dividing it into two chambers. 



168. This division commences the series of Algae with hollow, 

 more or less, external conceptacles, and is distinguished from 

 the others by its axial or suspended placenta. The frond is 

 opake and of a firm texture. They are, for the most part, 

 southern, tropical or sub-tropical Alg^ ; but Gelidium corneum, 

 the most variable, perhaps, of all plants, occurs in almost all 

 parts of the world, and is a very common British Algce. 

 Hypnea musciformis is also very widely diffused, but does 

 not come so far north as Great Britain. 



169. The hooked swollen tips of Hypnea are very curious, 

 and resemble greatly those of the threads in certain Fungi. 

 Gelidium cartilagineum, which is a very doubtful inhabitant 

 of our coasts, is remarkable for the various tints which it as- 

 sumes under varying circumstances. Originally of a dark 

 brownish purple red, on exposure to the air it changes, through 

 various brilliant tints of red, orange, yellow, and greenish, to a 

 horny white. Other species of this division have the same 

 property. In Hypnea the conceptacles contain numerous 

 roundish clusters of spores attached to anastomosing threads 

 which traverse their cavity ; in Gelidium the placenta assumes 

 the form of a dissepiment, attached only by the two edges, 

 but connected with the walls by forked threads.f The central 



* Voyage au Pole Sud, tab. 10, fig. 3. Rhodymenia ornata and Hom- 

 broniana, as figured in the same work, have very similar conceptacles. 



t See Dr. Harvey's figure of Nito'phyllum Gmelini, in Phyc. Brit. 

 tab. 235. The placenta, though in this case attached on either side, 

 has no connecting filaments. (Fig. 47, c, is not quite correct as to the 

 attachment. It was more evident in the drawing.) 



