Candolle, published in "Sur la durée relative de la faculté de germer des graines appartenant à diverses familles" (Annales des Sciences Naturelles; Botanique, 1846, III 6: 373-382); (translated title, "On the relative duration of the ability to germinate seeds belonging to various families") 1897 seed hygrometric studies by Victor Jodin (Annales Agronomiques, October 1897) 1912's Henry B. Guppy's 528 page "Studies in Seeds and Fruits- An Investigation with the Balance" (1912, London, England); subsequently reviewed in Science (June 1914, Washington, D.C.) Seed production Seeds are produced in several related groups of plants, and their manner of production distinguishes the angiosperms ("enclosed seeds") from the gymnosperms ("naked seeds"). Angiosperm seeds are produced in a hard or fleshy structure called a fruit that encloses the seeds for protection in order to secure healthy growth. Some fruits have layers of both hard and fleshy material. In gymnosperms, no special structure develops to enclose the seeds, which begin their development "naked" on the bracts of cones. However, the seeds do become covered by the cone scales as they develop in some species of conifer. Seed production in natural plant populations varies widely from year to year in response to weather variables, insects and diseases, and internal cycles within the plants themselves. Over a 20-year period, for example, forests composed of loblolly pine and shortleaf pine produced from 0 to nearly 5.5 million sound pine seeds per hectare. Over this period, there were six bumper, five poor, and nine good seed crops, when evaluated for production of adequate seedlings for natural forest reproduction. Development Angiosperm (flowering plants) seeds consist of three genetically distinct constituents: (1) the embryo formed from the zygote, (2) the endosperm, which is normally triploid, (3) the seed coat from tissue derived from the maternal tissue of the ovule. In angiosperms, the process of seed development begins with double fertilization, which involves the fusion of two male gametes with the egg cell and the central cell to form the primary endosperm and the zygote. Right after fertilization, the zygote is mostly inactive, but the primary endosperm divides rapidly to form the endosperm tissue. This tissue becomes the food the young plant will consume until the roots have developed after germination. Ovule After fertilization, the ovules develop into the seeds. The ovule consists of a number of components: The funicle (funiculus, funiculi) or seed stalk which attaches the ovule to the placenta and