Flora of North America: North of Mexico Volume 2: Pteridophytes and Gymnosperms (Flora of North America: North of Mexico)
Publisher: Oxford University Press, USA
Published: October 27, 1993
Language: eng
Number of pages: 496
ISBN-13: 9780195082425
First sentence: Characters used to circumscribe fern families often relate to cryptic features, e.g., presence or absence of annulus and its orientation, length and diameter (number of cells) of the sporangial stalk, nature of the spores (whether all one kind or dissimilar on a given plant), spore shape, color, ornamentation, and number per sporangium, stem and petiole cross-section anatomy, and adaxial grooving (or lack thereof) of the rachis and costae.