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Several species of green marine algae (Dasycladaceae) have been object of ecological investigations in recent years (Arasaki and Shihira-Ishikawa 1979; Cinelli, 1979; Liddle, 1979). Nevertheless, most data accumulated do not permit good estimation of their reproductive potential. This may be appraised by counting the total number of sporangia (S) and gametangia (cysts, C), assuming that the number of gametes (G) in the cysts does not undergo large variations. If all male and female gametes form pairs, the theoretical total number of zygotes (Z) per plant would be: Z = '/z SCG.Thus far the total number of sporangia and/or gametangia has not been counted because of technical difficulties. We found that photographic recording of fertile whorls of mature cells of Batophora oerstedii J. Agardh with a Polaroid camera mounted on a stereomicroscope permits rapid counting of the total number of sporangia. Mature B. oerstedii cells bear numerous fertile whorls serially distributed on the stalk (Fig. l a ) . In cells of similar length the number of whorls may vary from one individual to another (Hammerling, 1944). Moreover, under usual culture conditions, short cells (1-1.5 cm) have only 1-2 fertile whorls on the apical region of the stalk, with large sporangia (Fig. lb) . Figure 2 shows photographic recordings of the 14 fertile whorls of a normal Batophora oerstedii cell with a total of 214 sporangia. It clearly demonstrates that the number of sporangia per whorl varies considerably along the stalk. On the contrary, the number of hairs per whorl remains rather constant (7-8), with the exception of the apical whorl, which has 6 hairs only. The photographic recordings show that sporangia

Method for Rapid Counting of Sporangia in the Green Alga Batophora oersstedii