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THE SYSTEMATIC VALUE OF CUTICULAR CHARACTERS IN RECENT AND FOSSIL ANGIOSPERMS
Author(s) -
EDWARDS W. N.
Publication year - 1935
Publication title -
biological reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.993
H-Index - 165
eISSN - 1469-185X
pISSN - 1464-7931
DOI - 10.1111/j.1469-185x.1935.tb00492.x
Subject(s) - biology , botany , taxonomic rank , cuticle (hair) , biological classification , value (mathematics) , evolutionary biology , paleontology , mathematics , statistics , taxon
Summary. The study of cuticular structure as an aid to identification and classification, first extensively applied to fossil plants (particularly gymnosperms), is being increasingly used in recent taxonomic researches. The investigation of spodograms (the characteristic figures due to siliceous skeletons, crystals, and the like seen in the residue of leaves slowly reduced to ash) has proved of great value in the Gramineae especially, and among dicotyledons in the Urticales. Attempts to apply the method to fossil plants have not so far led to any results. Prat's analysis of epidermal characters in the Gramineae indicates the principles on which detailed taxonomic work should be based, and the systematic results he has so far obtained in this family are supported by evidence from other sources. Similar surveys of dicotyledonous families have scarcely yet been attempted; Bandulska's work on the Lauraceae is especially worthy of mention. The available evidence suggests that in cases of convergence of leaf form, structural differences in the cuticle will almost always provide a means of distinguishing isolated leaves. The distribution of cuticular elements may often furnish a means of discriminating closely related taxonomic groups which cannot be differentiated by purely structural characters. Statistical characters such as size or frequency of the elements, though often of value, must always be used with extreme caution. The ratio of stomata to epidermal cells (the stomatal index) is less variable than mere stomatal frequency. Individual cuticular and other epidermal characters cannot be considered in isolation in taxonomic work. As with other features used in classification, the sum of the available characters must be taken as the basis. The literature on fossil angiosperms, here summarised, is already extensive, particularly on the dicotyledons. Valuable results, however, can only be expected from full and detailed investigations of well‐preserved cuticles, together with a close comparison with a wide range of living forms.