tickseed sunflower: North American bur marigold with large flowers
bur marigold: any of several plants of the genus Bidens having yellow flowers and prickly fruits that cling to fur and clothing
blastula: early stage of an embryo produced by cleavage of an ovum; a liquid-filled sphere whose wall is composed of a single layer of cells; during this stage (about eight days after fertilization) implantation in the wall of the uterus occurs