favellrs terminate abbreviated lateral branchlets, and are surrounded by 

 several sharply serrated ramuli ; the serratures spiuous-tipped. The tetra- 

 spores are very small, and crowded in a dense sorus along the upper or 

 inuer edge of the pinnules, near their points. The colour, when quite 

 recent, is a full dark-red ; but 011 exposure to sun and air, and to fresh- 

 water, it becomes an intensely brilliant carmine, which is then preserved in 

 drying. The substance is cartilaginous, and the plant does not firmly adhere 

 to paper in drying. 



At first sight this beautiful species might almost be taken for 

 Phacelocarpus Bittardieri, so similar are its ramification and 

 colour ; but the structure of the frond, and the fructification, are 

 so different, that we are forced to refer these Algae to widely 

 separated families. Geologists sometimes complain that botanists 

 refuse definitively to name fossil plants whose impressions are 

 left on sandstone, and, in the geological sense, " well preserved ;" 

 but cases such as the present — and it is one of a thousand — show 

 how uncertain must be the " determination" even of the best 

 stone-printing of a fossil stem. What shall we say then of the 

 positive settlement of the affinities and structure of fossil sha- 

 dows, where there does not remain the faintest trace in stone of 

 the entity that " was and is not " ? 



Pt. Rhodocallis is as great a favourite with collectors in Aus- 

 tralia as Plocamium coccineum is in Britain, and for the same 

 reason. If the shore where it is lying be visited after a heavy 

 shower of rain, its intense carmine is sure to attract the most 

 careless eye ; but this colour, like that of Gelidium cartilagineum, 

 is due to the rain and sunshine, and after repeated washings 

 and sunnings the glories fade away. 



Fig. 1. Ptilota Biiodocallis, — the natural size. 2. A branchlet, bearing an 

 involucrate favella. 3. One of the teeth of the involucral leaflet. 4. A 

 favella, removed. 5. A pinnule, bearing a cluster of tetraspores. 6. A te- 

 traspore. 7. Longitudinal section of the frond. 8. Transverse ditto : — all 

 more or less magnified. 



