HELICOCYTIC AND ALLELOCYTIC STOMATA: UNRECOGNIZED PATTERNS IN THE DI COTYLEDON AE

Abstract

Two new mesogenous stomatal patterns are described for the Dicotyledonae: helicocytic, with a helix of four or more subsidiary cells surrounding the guard cell pair, and allelocytic, with an alternating complex of three or more C‐shaped subsidiary cells of graded sizes. The latter pattern may have guard cells developed parallel to the subsidiary cells (parallelocytic) or at right angles to them (diallelocytic). For both types, the complex development of regular sequences of mesogene subsidiary cells with particular attributes of size and arrangement provides strong probability of correlated ontogeny and adult pattern. They are related to mesogenous forms of the anisocytic, paracytic and diacytic patterns, but these latter may also be developed in different ways. The use of stomatal pattern data for taxonomic and evolutionary studies of dicote is discussed.