SOME PLANTS FROM TROPICAL SEA GARDENS 



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which the delicate root hairs penetrate the 

 calcareous sand and attach to themselves 

 small particles of this sand, thus making 

 anchorage hawsers in a bottom that is not 

 altogether stable. The rootlike part, in the 

 attached algae, is supposed to serve simply 

 as a holdfast. These sea plants often affix 

 themselves to smooth hard rock, or some- 

 times to pieces of iron or glass, from which 

 they can evidently draw little or nothing 

 in the way of nourishment. Their food is 

 apparently derived directly from the sur- 

 rounding water and air and is taken in 

 directly by the general surface of the 

 plant. In the case of these Udoteas and 

 their relatives, however, with their highly 

 developed systems of sand-burrowing rhi- 



zoids, it may be suspected that these 

 rhizoids play a part in the gathering of 

 food as well as in anchoring the plant. 

 What are commonly called "sea fans" by 

 frequenters of the sea are organisms of a 

 very different nature from those here de- 

 scribed under the name of mermaid's fan. 

 They are larger and are colonial animals 

 related to the corals. 



Another interesting and attractive mem- 

 ber of the group of lime-coated green algae 

 is the sea fir (Rhipocephalus phoenix), the 

 center of whose distribution appears to be 

 the Bahama Banks. This plant is usually 

 from two to six inches high and when grow- 

 ing on the sea bottom is very suggestive of 

 the little German Christmas trees that were 



THE MERMAID'S FAN, Udotea conglutina, from Bimini Harbor, Bahama Islands. (Natural size) 



