Abstract
An anatomical survey of 200 species in 22 genera of subtribe Pleurothallidinae (Orchidaceae) indicates which vegetative characters are of diagnostic value and at what taxonomic level. Most systematically useful characters are associated with the leaf, and include features of trichomes, cuticle, epidermis, hypodermis, spiral thickenings, and number of vein series. The secondary stem is of limited usefulness at higher levels. Number of velamen layers and protoxylem poles in the root may be reliable taxonomic indicators with certain limitations and precautions. The established subtribal phylogenetic trends of reduction in number of pollinia and specialization of the perianth may be correlated with particular anatomical trends, which are either reductionary also or involve specializations directly related to the water relations of the epiphytic habit.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
