Forty-nine taxa of Sansevieria were examined to provide the first detailed description ofleaf anatomy in the genus, as well as to determine the cellular organization of the water-storage tissue present in the central mesophyll ofall leaves. Leafform ranges from flat through cylindrical, with varying degrees ofxeromorphic characteristics, including cuticle thickness, stomatal depth, fiber content, and fiber cell development. Mesophyll in all species is divided into an outer region of chlorenchyma and a central region of colorless water-storage tissue. The water-storage tissue comprises a highly branched 3-dimensional network of living cells, among which are many dead, thin-walled water-storage cells. Species with more extreme xeromorphic characteristics tend to have a greater percentage of their water-storage tissue composed of water-storage cells. In 28 taxa, water-storage cells have spiral or reticulate wall bands. These taxa tend to be more xeromorphic. The wall bands may serve an important structural role in drought tolerance.;-a Leaf characteristics: f = flat, cr = crescentic, he = hemicylindrical, c = cylindrical, cc = cylindrical with adaxial channel, s = soft, h = hard, +/-= with or without wall bands in water-storage cells.
Forty-nine taxa of Sansevieria were examined to provide the first detailed description of leaf anatomy in the genus, as well as to determine the cellular organization of the water-storage tissue present in the central mesophyll of all leaves. Leaf form ranges from flat through cylindrical, with varying degrees of xeromorphic characteristics, including cuticle thickness, stomatal depth, fiber content, and fiber cell development. Mesophyll in all species is divided into an outer region of chlorenchyma and a central region of colorless water-storage tissue. The water-storage tissue comprises a highly branched 3-dimensional network of living cells, among which are many dead, thin-walled water-storage cells. Species with more extreme xeromorphic characteristics tend to have a greater percentage of their water-storage tissue composed of water-storage cells. In 28 taxa, water-storage cells have spiral or reticulate wall bands. These taxa tend to be more xeromorphic. The wall bands may serve an important structural role in drought tolerance.
Fifty‐three species of Selaginella were examined for variations in microsporangium anatomy and microspore dispersal strategies. Five anatomically different kinds of microsporangia were observed, displaying three different strategies for microspore dispersal. Xeric species, including all isophyllous species, have microsporangia that only dry and shrink as they dehisce, resulting in microspores being passively dispersed. Among anisophyllous species from tropical and subtropical habitats some species actively eject their microspores, while others of the series Articulatae eject the entire microsporangium. These two types of active ejection both utilize a mechanism similar to that found in fern leptosporangia.
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