Evolutionary history of plants and radially symmetrical, is an integumented megasporangium surrounded by a cupule. The megasporangium bears an unopened distal extension protruding above the multilobed integument. It is suspected that the extension was involved in anemophilous pollination. "Runcaria" sheds new light on the sequence of character acquisition leading to the seed. "Runcaria" has all of the qualities of seed plants except for a solid seed coat and a system to guide the pollen to the ovule. The first spermatophytes (literally: "seed plants") – that is, the first plants to bear true seeds – are called pteridosperms: literally, "seed ferns", so called because their
The Different Forms of Flowers on Plants of the Same Species The Different Forms of Flowers on Plants of the Same Species The Different Forms of Flowers on Plants of the Same Species is a book by Charles Darwin first published in 1877. It is the fifth of his six books devoted solely to the study of plants (excluding "The Variation of Animals and Plants under Domestication"). These writings contributed to Darwin's pursuit of evidence that would support his theory of natural selection. There were only two more books to follow: "The Power of Movement in Plants" (1880) and "The Formation of Vegetable Mould through the Action of Worms" (1881). He