recommended as a companion plant to the tomato. Common claims are that basil may deter pests or improve tomato flavor. However, in double-blind taste tests, basil did not significantly affect the taste of tomatoes when planted adjacent to them. Tomato plants can protect asparagus from asparagus beetles, because they contain solanine that kills this pest, while asparagus plants contain Asparagusic acid that repels nematodes known to attack tomato plants. Marigolds also repel nematodes. Pollination In the wild, original state, tomatoes required cross-pollination; they were much more self-incompatible than domestic cultivars. As a floral device to reduce selfing, the pistil of wild tomatoes extends farther out of the flower than today's cultivars. The stamens were, and remain, entirely within the closed corolla. As tomatoes were moved from their native areas, their traditional pollinators (probably a species of halictid bee) did not move with them. The trait of self-fertility became an advantage, and domestic cultivars of tomato have been selected to maximize this trait. This is not the same as self-pollination, despite the common claim that tomatoes do so. That tomatoes pollinate themselves poorly without outside aid is clearly shown in greenhouse situations, where pollination must be aided by artificial wind, vibration of the plants (one brand of vibrator is a wand called an "electric bee" that is used manually), or more often today, by cultured bumblebees. The anther of a tomato flower is shaped like a hollow tube, with the pollen produced within the structure, rather than on the surface, as in most species. The pollen moves through pores in the anther, but very little pollen is shed without some kind of externally-induced motion. The ideal vibratory frequencies to release pollen grains are provided by an insect, such as a bumblebee, or the original wild halictid pollinator, capable of engaging in a behavior known as buzz pollination, which honey bees cannot perform. In an outdoors setting, wind or animals usually provide sufficient motion to produce commercially viable crops. Fruit formation Pollination and fruit formation depend on meiosis. Meiosis is central to the processes by which diploid microspore mother cells within the anther give rise to haploid pollen grains, and megaspore mother cells in ovules that are contained within the ovary give rise to haploid nuclei. Union of haploid nuclei from pollen and ovule (fertilization) can occur either by self- or cross-pollination. Fertilization leads to the formation of a diploid zygote that