The Cheilanthes dichotoma Group of South America

Volume: 79Start Page: 127End Page: 13

Austrostrobus ornatum. Nov, gen, et sp.. cono petrificado de Lycopsida del Triásico de Santa Cruz. (Argentina)

En 1962, en su análisis de las tafofloras paleozoicas y mesozoicas, Archangelsky señalaba la ausencia de Lycopsida en el Triásico gondwánico. Poco después, esta situación se modificó como consecuencia del descubrimiento de Cylostrobus Helby et Martin (1965) proveniente de estratos asignados al Triásico inferior de Australia. Hace algo más de un año, en ocasión de hallarnos revisando la Colección Paleobotánica, el Dr. S. Archangelsky y uno de los autores (B.P.), encontramos una pieza petrificada que atrajo mucho nuestra atención. Examinada bajo la lupa se concluyó que se trataba de una fructificación, presumiblemente de Lycopsida, cuya proveniencia indicaba: provincia de Santa Cruz, Triásico. Con el objeto de precisar la ubicación geográfica y estratigráfica de la pieza, se efectuaron consultas con elDr. M, Sarris. El material proviene de la Fm. El Tranquilo, unidad litoestratigráfica que se ubica actualmente en el Triásico superior

Structure of the Pollen Exine of Rhoiptelea chiliantha

The exine of mature pollen grains of Rhoiptelea chiliantha was studied. The size of the pollen grains is about 23 by 27 μm. They are tricolporate with short colpi that are 1-2 μm wide and 10-12 long. The spinules of Rhoiptelea are similar in form and size to those of Gentianales. The spinules consist of rods of ca 70 nm in width. These rods are evident throughout the tectum and columellae. The columellae are of two distinct sizes. The smaller ones are ca 70 nm wide and join the tectum and the larger columellae. These larger ones appear to be composed of several 70 nm in width rods. They join the distal surface of the foot layer. The proximal surface of the foot layer is marked by a white line (referred to as a junction plane) where it joins the endexine. The endexine consists of a solid-appearing component adjacent to the foot layer (referred to as endexine-1) and laminar components (endexine-2) that are attached to and apparently become a part of endexine-1. There is no indication of an arcus. In well preserved grains the aperture is covered by an operculum or operculum-like component. In well-rehydrated pollen grains there is an oncus of considerable complexity under the aperture and over the intine. The Ubisch bodies have an exine ornamented with widely-spaced spinules like the spinules on the pollen exine

Wall Structure During Stages in Development of Selaginella pulcherrima and S. haematodes Megaspores

There are hundreds of exospore units that extend across the gap and into the mesospore in middle stages in megaspores of Selaginella pulcherrima Liebm.ex Fourn and S. haematodes (Kunze) Spring. The mesospore of these megaspores is resistant to acetolysis during middle stages suggesting the presence of sporopollenin. There are also spheroidal structures that are resistant to acetolysis on the surfaces of the outer and inner exospore in both species in middle and mature stages. In late stages the mesospore no longer exists and the inner exospore is a narrow stripe, i.e., there is no longer a space (gap) between outer and inner parts of the exospore. Our interpretation for the loss of the mesospore is that sporopollenin does not become polymerized under physiological conditions to its exceptional state of resistance to reduction, but does so when exposed to native or experimental oxidation; in our case, exposure to the atmosphere by cutting open the megaspore and plunging it into the acetolysis mixture

Palynological analysis of Dennstaedtiaceae taxa from the Paranaense Phytogeografic Province that produce monolete spores and its systematic implications (I): Blotiella lindeniana , Histiopteris incisa and Paesia glandulosa

ABSTRACT The genera of Dennstaedtiaceae have sporophytes with very different morphological characteristics between each other, and this feature has made difficult the systematic circumscription of the family. This reason makes necessary the study of new characters that allow a better understanding of the relations within the group. The spore morphology and wall structure of Blotiella lindeniana, Histiopteris incisa and Paesia glandulosa from the Paranaense Phytogeographic Province were studied using light microscope, and scanning and transmission electron microscope. The exospore has two layers and, according to the species, the exospore surface bears pila, echinae, verrucae, bacula and tubercles. The perispore has two or three layers and its surface is psilate, baculate or rugulate. The variability found in the sculpture of the spores and their stratification and ultrastructure of perispore reflects the morphological differences observed in the sporophyte of the species studied. Additionally, while the stratification and ultrastructure of the exospore is shared by the Dennstaedtiaceae species, their ornamentation could be a character to distinguish species into the clade “hypolepidoide”. The finding of spores with similar characteristics in phylogenetically unrelated families allows us to suggest that palynological features do not have an evolutionary value to establish relationships between groups above the genus level

Novedades en la Distribución de las Cyatheaceae (Pteridophyta) en Argentina Novelties in the distribution of Cyatheaceae (Pteridophyta) of Argentina

Cyathea atrovirens (Langsd. & Fisch.) Domin se cita por primera vez para la provincia de Corrientes (Argentina). De esta manera se extiende su área de distribución hacia el sudoeste. Además se confirma la presencia de Alsophila odonelliana (Alston) M. Lehnert en la provincia de Jujuy (Argentina). En este estudio los caracteres de las esporas resultaron diagnósticos para la determinación genérica de los taxa.<br>Cyathea atrovirens (Langsd. & Fisch.) Domin is reported for the first time for Corrientes province (Argentina). Thus, its area of distribution is extended southwest. The presence of Alsophila odonelliana (Alston) M. Lehnert is confirmed for Jujuy province (Argentina). In this study the spore features were diagnostic in order to determine these taxa