An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for a minimum of a part of its life cycle without causing apparent disease. Endophytes are ubiquitous and are found altogether species of plants studied to date; however, most of the endophyte/plant relationships aren't well understood. Some endophytes may enhance host growth, nutrient acquisition and improve the plant's ability to tolerate abiotic stresses, like drought, and reduce biotic stresses by enhancing plant resistance to insects, pathogens and herbivores. Endophytes could also be transmitted either vertically (directly from parent to offspring) or horizontally (among individuals). Vertically transmitted fungal endophytes are typically considered clonal and transmit via fungal hyphae penetrating the embryo within the host's seeds, while the reproduction of the fungi through asexual conidia or sexual spores results in horizontal transmission, where endophytes may spread between plants during a population or community.