urceolate, with a prominent orifice. Tetraspores abundantly formed on 

 the bars of the network, spherical, ternately parted. Colour variable ac- 

 cording to the age or freshness of the specimen ; when quite fresh it is 

 greenish-purple, reflecting iridescent tints ; on exposure, or in fresh-water, 

 it rapidly assumes a brighter red, and sometimes becomes rosy or blood- 

 red. Substance very delicate, soon decomposing in fresh- water. In drying 

 the frond closely adheres to paper. 



This delicately-beautiful Alga is by no means rare at Rott- 

 nest Island, after winter gales, being cast up on most of the 

 sandy beaches to the west of the pilot's house. It grows on 

 rocks, just below low-water mark, at the little cove called " Bag- 

 dad," and elsewhere. 



As a species, it is readily known from the other Australian 

 kinds by its toothed or ciliate margin, and by the dark, often 

 livid colour, when fresh. It is also of thinner substance, and 

 more densely tufted than the others. Indeed, it is much more 

 nearly allied to the Ceylon M. fragilis than to the Australian 

 species, and perhaps it may not always be clearly distinguish- 

 able from that plant. Generally the margin and colour define 

 it, but specimens sometimes occur in which the toothing is 

 obsolete and the colour bright. I have not seen it forming glo- 

 bular tufts, as II. fragilis does ; but such a character is hardly 

 specific, and the external form is so varied in different speci- 

 mens from the same beach, that it gives us little aid. 



Fig. 1, 2, 3, different varieties of Mautensia denticulata, — the natural size. 

 4. Portion of the lamina, showing the toothed margin, and part of a net- 

 work. 5. Small portions of a network, bearing tetraspores on the longi- 

 tudinal bars. 6. Tetraspores 2« s«7«. 7. Surface-cells from the basal por- 

 tion of the frond : — the latter figures variously vuujnijied. 



