A CALCIFIED AND SEGMENTED GREEN SEAWEED, Halimeda simulans, from Porto Rico. 



(About four fifths natural size) 



once sold in this country for holiday deco- 

 rations. It is dark green when living but 

 is soon bleached to a chalky white after 

 being killed and exposed to the light. In 

 general structure, it is somewhat interme- 

 diate between the brushes and the fans, 

 being brushlike in general habit but hav- 

 ing numerous small overlapping fans for 

 branches. 



The writer once enjoyed the privilege of 

 being becalmed for two days on the 

 Bahama Banks in a small sloop. On these 

 banks are hundreds of square miles where 

 the water is mostly from one to twenty 

 feet deep. The bottom here is chiefly of 

 more or less compacted oolitic sand, con- 

 sisting of clean white nearly spherical 

 granules that suggest fish roe both in form 

 and size. Such a bottom rarely becomes 

 muddy to any appreciable extent and the 

 waters above it are wonderfully clear, so 

 much so that when a breathless calm makes 

 the surface of mirror-like smoothness one 

 can see the vegetation and animal life of 

 the sea bottom in twelve or twenty feet of 

 water almost as distinctly as if the water 

 were only two feet deep. On wide areas of 



564 



the Bahama Banks the merman's shaving 

 brushes, the mermaid's fans, the sea firs, 

 and their relatives are the dominant fea- 

 tures of the marine flora, sometimes forming 

 a continuous carpet on the floor of the sea. 



Prominent among the relatives of the 

 Udoteas are eight or ten kinds of Hali- 

 meda, in all of which the calcified plant 

 body is regularly jointed or segmented. In 

 most of the species of this genus the lime 

 is abundant and the system of joints gives 

 a certain degree of flexibility to a plant 

 that would otherwise be quite rigid and 

 stonelike. One of the species, at least, 

 sometimes occurs in great masses, and the 

 quantities of lime left by its decay are, in 

 places, important factors in reef building 

 and land forming. The fact that it is a 

 more rapid grower than the corals seems to 

 give it a certain advantage over them in 

 the matter of secreting and depositing 

 lime, even though the proportion of lime 

 in its make-up is not so great. 



Perhaps the most dainty and exquisite of 

 the green algae is the mermaid's wineglass, 

 Acetabulum crenulatum, which grows in 

 shallow bays and protected places, ranging 



