Table 4.

Change in heterocyst frequency of a cyanobacterial photobiont with distance from a green algal photobiont

Heterocyst frequency (%)
	Distance to green algal photobiont
Associations	5–10 mm	0–2 mm
Pseudocyphellaria rufovirescens	7·4 ± 0·2	14·8 ± 0·9
Dendriscocaulon umhausense/Lobaria amplissima*	1·9, 2·5, 4·0. 5·7	10·2, 15·2
Solorina spongiosa*	5·8, 4·9, 7·1	28·3, 43·1, 45·5, 54·7
Sticta dufourii/S. canariensis*	3·1, 4·1	12·4, 13·3, 18·0

* Data from Hitch and Millbank (1975b); frequencies are individual counts.