HYBRIDS IN PLANTS. A hybrid may be defined as a cross between two parents be longing to different varieties or different spe cies. In a few cases, two different genera have been crossed. Thus, it is evident that the term, hybrid, is used whenever the two parents do not belong to the same species or variety. Con sequently, a hybrid differs from the result of ordinary fertilization only in the fact that the two parents are not so closely related. When hybrids are produced artificially, the pollen from one parent is placed upon the stigma of the other parent, great care being taken to ex clude all other pollen. When the parents arc dicecious — the male bearing only anthers with pollen, and the female only ovaries tipped with stigmas — it is easy to exclude other pollen by placing a paper bag over the female flowers. When the anthers and ovaries are on the same plant, but in different flowers — as in corn, where the tassel bears the anthers and the silk is tipped with the stigmas — there is little diffi culty in making a cross. The tassel of the plant to be used as the female parent is cut off before it ripens any pollen; a tassel from the male parent is shaken over the silks of the female until the silks are well dusted with pol len; a paper bag is then placed over the silks. It is an interesting fact that in corn, the male parent determines whether the content of the grain is to become starch or sugar, i.e., whether there is to be "sweet corn" or "field corn"; so that sweet corn may be raised on a plant field corn seed, and vice-versa. When the two parents, anthers (male) and ovaries (female), are in the same flower, as in lilies and most flowers, the anthers of the flower to be used as the female parent must be removed before they ripen their pollen,. lest
"close fertilization)) might result. The stigma is then dusted with pollen from the male parent, and a paper bag is applied. While nu merous hybrids occur in nature, artificial hy bridization is of immense importance, economi cally, in developing new forms better suited to local conditions, since desirable features of different graces,* or varieties, as vari ous degrees of close relationship are denomi nated, may be combined by judicious crossing.
The term, graft hybrid, has become fixed in the literature of the subject. As the name implies, it is a hybrid secured by grafting. Such hybrid, have been know.n for nearly 100 years; but they have more recently come into prominence through the researches of Winkler, who succeeded in grafting the nightshade (So lanum nigrum) upon the tomato (Solarium ly topersicum) The resulting form had sonic leaves like those of the nightshade and some like those of the tomato and still others showed mixed characters; altogether, the ((hybrids was so bizarre that it was called a chimera. It is now believed that such chimeras are not the result of any blending of characters but that they are built up of pure cells of the two 'parents,'" so that the chimera may be re garded as a mosaic built up of two kinds of blocks, the cells representing the blocks. Con sult Winkler, H., 'Untersuchungen uber Propf bastarde) (Jena 1912). A review, with refer ences, may be found in the Botanical Gazette (Vol. LI, 1911, p. 147).