A variety of fossil plants from Devonian to Permian rocks of 10 localities in England and eastern North America were analyzed for residual carbohydrates. There seems to be little if any difference in the carbohydrate components of the psilophytes and lycopods studied and those of modern pteridophytes. The greater quantity of D.galactose in fossil Equisetales than in modern examples suggests a change from important amounts of galactan structural polysaccharides to mainly glucans (such as cellulose) in modern Equisetum. An evolutionary change in the gymnosperm Cordaites between Devonian and Pennsylvanian time may have involved a shift from galactan-rich, algal-type structural polysaccharides to cellulose.

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