Page 107 - Visions of the Future Chemistry and Life Science

96 A. R. HEMSLEY AND P. C. GRIFFITHS

Figure 6.1. All scales refer to bar in (b). (a) The silica frustule (shell) of the colonial
diatom Actinoptycus. Microscopic algae may use silica, calcium carbonate, or
organic polymers to produce such shells. Scale 10 m. (b) Pollen grains of the
Morning Glory, Ipomoea indica, have a complex surface pattern. Such patterns are
common among spores and pollen, but how do they arise? Scale 40 m. (c) A
broken section of a spore wall from Selaginella myosurus (a type of club moss)
showing complex internal structure including a colloidal crystal region composed
of numerous tiny spherical particles. It is spore walls such as these that have led
botanists to consider colloids as fundamental in the production of complex wall
patterns.