158 L. HILLIS-COLINVAUX 



with the production of more than one vegetative generation. Only the 

 completion of the sexual cycle, with the development of the charac- 

 teristic segmented thallus from the loose filaments obtained by the 

 germination of zygotes (Meinesz, 1972b), still remains to be carried out 

 in culture. 



The basic approach, which can be modified in many ways to suit 

 facilities and the particular problem being investigated, is given in the 

 following subsections. Considerably more elaborate arrangements are 

 possible and may at times be feasible, but much can be done simply. 

 Halimedae and their calcareous relatives such as Penicillus, Udotea, 

 Bhipocephalus, Acetabularia and Batophora all seem relatively hardy. 

 They can be transported for several days in dim light and at tempera- 

 tures of 20 °C or less, and still grow satisfactorily in the laboratory. 



It is not yet possible to begin Halimeda cultures with clean zygotes, 

 not only because fertile plants of most species are hard to find, but also 

 because it is not yet known how to germinate and grow the mature 

 thallus from zygotes. It is only with tuna from the Mediterranean that 

 development beyond the zygote has been obtained (Meinesz, 1972b), 

 and this has not been the adult plant as we know it (Section VII). It is 

 necessary, therefore, to begin cultures with direct transplants from the 

 sea, a procedure that unavoidably introduces troublesome contaminants 

 into the cultures. The basic procedure is to collect good field material, 

 to clean it by hand, to plant it in simple aquaria, to bubble air into the 

 water, to provide light and to combat epiphjrtes. 



A. Field procedure 



It is obviously important to select healthy vigorous specimens; 

 the difficulty is to identify the signs of vigour and health. It seems 

 natural to avoid thalli with segments which tend to fall off when 

 touched, with white segments, or with large numbers of epiphytes. The 

 thalli selected should be collected with minimal damage to the holdfast, 

 and rock-growing species should have a portion of the rock to which the 

 holdfast is attached included if possible. 



After collecting, the thalli are carefully cleaned of as much associated 

 plant or animal material as is possible without breaking the segment 

 surface or pulling away the holdfast filaments. Then, until the algae can 

 be transported to home base, they are maintained in three to four times 

 their volume of clear seawater at about 24-25 °C with a bubbler, and 

 exposed to diffuse light. For travel, the water is replaced with fresh 

 clean seawater, the amount being decreased to that manageable for the 

 journey, and the containers closed. If accessible, compressed air is 



