Table 1.

Shape, range of linear dimensions and surface area:volume ratio (SA:V) of three species of Nostoc colonies, Nostoc trichomes, submerged leaves and single phototrophic unicells

Species and phototrophic type	Shape	Diameter/thickness (cm)	SA:V (cm–1)
N. commune	Flat structure	0·1	10 to 20
		0·5	2 to 4
N. pruniforme	Sphere	0·2	30
		17·0	0·36
Nostoc zetterstedtii	Sphere, granulated surface	0·2	30
		7·0	0·85–1·7
N. trichomes	Cylinders	5 × 10–4	8000
		10 × 10–4	4000
Submerged leaves	Flat structure	1 × 10–3	2000
		30 × 10–3	70
Single-celled algae or cyanobacteria	Sphere	2 × 10–4	30 000
		2 × 10–3	3000