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Abstract

In this Article the growthform of Bulbostylis leucostachya is analysed in comparison with that of other tropical arboriform Cyperaceae, particularly, Cephalocarpus dracaenula Nees, and Bulbostylis paradoxa (Spreng) Lindm. It is also compared with the growthform of Vellozia litophila Schultes. For each comparison, similitudes and divergences of the architectural features are determined; relationships between architectural features with climate and habitat are emphasized. B. leucostachya pseudocaules are produced by cladogenic roots and the remanent hardened leaf sheaths, together; therefore, its diameter increases basipetally, contrary to what happens in most Monocotyledons, as new cladogenic roots are being incorporated. Cladogenic roots originate very near the vegetative shoot of each pseudocaule branch. Shoot axis, cladogenic roots and leaf sheaths do not persist for long time, soon or later they die off; being this the reason why the proximal region of pseudocaule is dead; so that the main function of pseudocaule may consist in giving mechanical anchorage to the whole plant and support to the terminal leaf rosette where living tissues and meristems are located.

These latter tissues are dormant during the dry season and reactivate when the rainy season begins. Both, remanents of leaf sheaths and sheath hairs can retain rainwater and water vapor as well, due to the so-called sponge-effect. It is supposed in this paper that water supply to living tissues of the plant should take place through such hairs and young roots. It seems that for these plants, growing on the bare surface of granitic rocks, there is not apparently another possibility. The notably xeromorphic leaf blade structure supports also this hypothesis.