Fern plants. Like all other vascular plants, the diploid sporophyte is the dominant phase or generation in the life cycle. The gametophytes of ferns, however, are very different from those of seed plants. They are free-living and resemble liverworts, whereas those of seed plants develop within the spore wall and are dependent on the parent sporophyte for their nutrition. A fern gametophyte typically consists of: Ferns first appear in the fossil record in the early Carboniferous period. By the Triassic, the first evidence of ferns related to several modern families appeared. The great fern radiation occurred in the late Cretaceous, when
Second-generation immigrants in the United States conflict between that of their parents and that of mainstream U.S. society. The process by which these second-generation immigrants assimilate into society is increasingly being researched, and multiple theories on the cultural assimilation of second-generation immigrants have been proposed. The theory of segmented assimilation for second-generation immigrants is highly researched in the sociological arena. Segmented assimilation focuses on the notion that people take different paths in how they adapt to life in the United States. This theory states that there are three main different paths of assimilation for second-generation immigrants. Some immigrants assimilate smoothly into the white middle class of