An Attempt to Clarify the Term Croton-Pattern with Emphasis on Lasiosiphon kraussianus (Meisn.) Burtt. Davy (Thymelaeaceae)

Objectives: The present study aims to establish the nature of the fine structures of the exine which account for the distinctive croton-pattern in Lasiosiphon kraussianus. Methods/Statistical Analysis: Light (LM), scanning electron (SEM) and transmission electron microscopic (TEM) studies on Lasiosiphon kraussianus (Meisn.) Burtt. Davy pollen grains were examined and illustrated in an attempt to elucidate its exine pattern. Previous descriptive terms used for similar exine pattern were reviewed with special emphasis on the terms croton-pattern, retipilate and reticulum cristatum. Findings: The exine pattern in L. kraussianus was interpreted as having mixed croton-pattern and micro-echinate sculpturing. The columellae (structure) are branched and fused together forming a reticulum some distance beneath the surface. Supratectal pila are regularly arranged in ring-like patterns with narrower foveolae. Application/Improvements: The results clarified the confusion and/or misuse encountered in previous works in the terms croton-pattern, retipilate and reticulum cristatum, and provided an accurate description for Lasiosiphon kraussianus.