Ovule, seed and seedling characters in Acharia (Achariaceae) with evidence of myrmecochory in the family

An investigation of mature seed structure in Guthriea capensis and ovule-to-seed development in Acharia tragodes indicate that the two species are herbaceous myrmecochores with similar adaptations for seed dispersal and germination. The development and structure of the modified seed tissues, namely a sarcotestal elaiosome, a fringe layer in the mesotesta, endotestal-exotegmic mechanical layers and a chalazal seed lid are described. Additional embryological similarities between the two taxa include, amongst others, sessile ovules, distally lobed outer integuments, zigzag micropyle canals formed by both integuments, bisporic Allium Type embryo sacs, suspensorless embryos belonging to the Penaea Variation of the Asterad Type, and small embryos in the mature seed. In Acharia intraseminal embryo growth occurs before radicle emergence, germination is epigeal and seedlings belong to the Macaranga Type

Broad-scale patterns of body size in squamate reptiles of Europe and North America

Aim To document geographical interspecific patterns of body size of European and North American squamate reptile assemblages and explore the relationship between body size patterns and environmental gradients. Location North America and western Europe. Methods We processed distribution maps for native species of squamate reptiles to document interspecific spatial variation of body size at a grain size of 110 x 110 km. We also examined seven environmental variables linked to four hypotheses possibly influencing body size gradients. We used simple and multiple regression, evaluated using information theory, to identify the set of models best supported by the data. Results Europe is characterized by clear latitudinal trends in body size, whereas geographical variation in body size in North America is complex. There is a consistent association of mean body size with measures of ambient energy in both regions, although lizards increase in size northwards whereas snakes show the opposite pattern. Our best models accounted for almost 60% of the variation in body size of lizards and snakes within Europe, but the proportions of variance explained in North America were less than 20%. Main conclusions Although body size influences the energy balance of thermoregulating ectotherms, inconsistent biogeographical patterns and contrasting associations with energy in lizards and snakes suggest that no single mechanism can explain variation of reptile body size in the northern temperate zone

Germination of the fruits of Leucadendron tinctum

The pericarp and the embryo contribute to the dormant condition of achenes of Leucadendron tinctum. The pericarp apparently mechanically restricts embryo growth and to a lesser extent acts as a barrier to oxygen movement to the embryo. Dormancy is effectively overcome by scarification, stratification and treatment with hydrogen peroxide. Germination was inhibited and cytokinin levels were low in intact achenes subjected to elevated oxygen partial pressures. S. Air. J. Bot. 1985, 51: 448–452Die saadhuid en die embrio dra by tot die rustoestand van Leucadendron tinctum-vrugte. Die saadhuid beperk waarskynlik embriogroei meganies en beïnvloed tot ‘n mindere mate die beweging van suurstof na die embrio. Saadrus kan doeltreffend opgehef word deur skarifisering, stratifisering en behandeling van die vrugte met waterstof-peroksied. Ontkieming is geïnhibeer en sitokinienvlakke was laag in heel vrugte wat aan verhoogde suurstof-konsentrasies blootgestel is. S.-Afr. Tydskr. Plantk. 1985, 51: 448–45