Probable Fertile Region of Asteroxylon mackiei K. and L.
Asteroxylon mackiei was first described from the Rhynie Chert by Kidston and Lang1, but the nature of its reproductive region has remained uncertain, since the peculiar leafless axes and small pear-shaped sporangia, which they provisionally assigned to the plant, have never been found connected to its leafy stems.
The Rhynie cherts: an early Devonian ecosystem preserved by hydrothermal activity.
The Rhynie cherts contain a remarkable early Devonian terrestrial to freshwater biota preserved in siliceous sinter by the action of a precious-metal-bearing hot spring system. Arthropods, vascular and non-vascular plants, algae, fungi and cyanobacteria are present. Preservation ranges from perfect 3D cellular permineralization to compacted coalified films, and can be related to both silicification processes and stages of biological and physical degradation of the plants at the time of silicification. Plants occasionally have original subaerial vertical axes preserved in growth position, and rhizomes bearing rhizoids. The plant litter of the substrate is also partly silicified. Silicification of organic material took place in hot spring pools, by surface flooding of areas with growing plants, and by permeation of the substrate. Sinters recognized include botryoidal geyserite typical of vent margins, and laminated sinter comparable with that of modern sinter terraces. Massive, vuggy, brecciated and nodular sinter textures are also present. At the microscopic level, textures associated with filamentous elements of the biota, and with the preservation of plants, closely match those present in modern sinters. Oxygen isotope and organic geochemical data from the Rhynie cherts indicate a temperature of 90-120 degrees C. This is apparently greater than the temperature at which elements of the biota were preserved and represents subsequent shallow burial in the hot spring system. The range of temperature and chemistry present at the surface provided high local environmental gradients. Current work attempts to identify thermophilic elements of the biota and document environmental zonation of biota relative to hot spring vents.
The Inca Occupation of the South Coast of Peru
like the others, however; it forks into several nearly parallel ravines of which the largest are Huayuri, Rio Grande-Palpa, Ingenio (called Collao in ancient times), Nasca proper (the ancient Caxamarca), Taruga, and Poroma. Due to peculiarities of the local topography, the irrigated areas in Ica and the ravines of Nasca are located inland, at the foot of the mountains, rather than at the mouths of the rivers as is more usual in Peruvian coastal valleys. No sharp natural or cultural boundary separates the valley of Chincha from the valleys of Cafiete (ancient Huarco and Runahuana), Asia, and Mala, the next valleys going up the coast to the northwest. At the other end of the area we are considering, however, there is a sharp break; beyond Yauca the Andean foothills reach out to the sea, natural conditions are quite different, and there are important differences in the archaeological picture as well. The historical sources which mention the south coast are not particularly helpful, except in so far as they provide us with a few dates. To begin with, no chronicler gives an explicit account of the political organization of the south coast at the time it came into contact with the Incas. It can, perhaps, be inferred from Cabello Balboa's statements about common policy toward the Inca invaders that there was some sort of political connection between the valleys of Mala, Cafiete, and Chincha, but the connection need have been no more than a temporary military alliance. Cabello makes no mention at all of Pisco. The valleys of Ica, Nasca, and 125