ECOLOGY AND TAXONOMY OF Holimeda 159 



bubbled in at this stage. Large heavy-gauge plastic bags are useful for 

 separating different collections, those with and without attached pieces 

 of rock, for example. The bags can then be tied off and arranged care- 

 fully in stjrrofoam chests to minimize damage. Buckets with fitted lids 

 and collapsible carboys are also suitable containers, and can be carried 

 in the pressurized cabins of aircraft. About 50 sand-dwelling Halimedae 

 can be transported in a 4-5 1 carboy half-full of seawater. They survive 

 up to 3 days of travel in this way. 



The algae are replanted as soon as possible after arrival. If time and 

 facilities permit, it is a good plan to check for smaller epiphytes with a 

 dissecting microscope and remove them. 



B. Basic laboratory 'procedure 



The Halimedae are grown in closed aquaria without recirculating 

 water, lighted for part of the day, provided with about 2-5 cm of 

 calcareous gravel, and equipped with an air bubbler (Fig. 50). Sand- 

 dwelling forms with bulbous holdfasts are simply planted in aquaria 

 containing about 2-5 cm of sand over the calcareous gravel. Rock- 

 attached forms are anchored to the bottom or suspended from an 

 arrangement of rocks or pieces of clean dead coral in a manner that 

 resembles their normal growth habit. Species with a sprawling growth 

 pattern such as opuntia are merely placed in an aquarium without sand 

 but which usually contams chunks of rock or coral (Fig. 51). The 

 aquaria are covered with glass or a thin sheet of transparent plastic. 

 The thalli are regularly cleaned by hand of epiphytes and animals as far 

 as is possible without damaging them. 



1. Culture medium 



Natural seawater and the commercial artificial seawater "Instant 

 Ocean" have been the main media used. 



Natural seawater is collected from areas free of wastes and filtered 

 through a Millipore filter with average pore size 0-45 ^m. 



Commercial artificial seawaters were not available when I first 

 started culturing. They are now readily obtainable, however, and have 

 proved as satisfactory for this work as natural seawater. The compo- 

 sition of "Instant Ocean" is given in Table XL Some minor elements 

 are missing from it, but results seem comparable to those with natural 

 seawater. 



No nutrients are added directly to either medium in routine cultur- 

 ing. Some nutrients are probably introduced by the sand substrates, 



