Watermelons are one of summer’s most refreshing fruits, but their contents often lead to confusion regarding what is and is not a true seed. The appearance of these internal structures varies widely, primarily due to differences in maturity and the specific type of watermelon. Understanding the visual characteristics of both the mature, viable seeds and the soft, white structures found in popular hybrid varieties helps distinguish between the two.
Visual Characteristics of Mature Watermelon Seeds
The fully developed seeds found in traditional watermelons are easily recognizable. These mature seeds are typically a dark, uniform color, ranging from black to a deep brown, though some varieties may exhibit a mottled or patterned appearance with tan or reddish markings. The dark pigmentation is the result of a hardened, fully matured outer seed coat, known as the testa.
These viable seeds have an oblong, flattened shape with a smooth, hard texture that provides a protective casing for the internal embryo. A mature seed generally measures between 7 to 10 millimeters in length and 4 to 6 millimeters in width, though size can vary significantly between cultivars. The primary function of this robust structure is germination; if planted under the proper conditions, these dark, fertile seeds will sprout into a new watermelon plant. Their durable shell gives them a firm, slightly crunchy texture if chewed, which is why they are often spit out when consuming the fruit.
While all watermelon seeds begin small and white, only those that fully mature develop the dark color and tough exterior necessary for survival and planting. These characteristics are found in diploid watermelons, which are the standard variety with two sets of chromosomes.
Understanding the White Ovules
The small, soft, white structures found throughout the flesh of “seedless” watermelons represent a different stage of development. These are not fully matured seeds but are actually undeveloped ovules or empty seed coats. They remain white because the process of maturation, which includes the hardening and darkening of the outer shell, was genetically interrupted.
Seedless watermelons are a sterile hybrid known as triploids, created by crossing a diploid plant with a tetraploid plant. This process results in a fruit with three sets of chromosomes, which prevents the ovules from developing into viable, fertile seeds. Consequently, these white ovules are infertile and cannot germinate if planted.
The appearance of these ovules is soft, translucent, and slender, lacking the hard, protective shell of a mature seed. Because of their undeveloped state, they are easily chewed and swallowed, often going unnoticed while eating the fruit. Their presence is a natural outcome of the hybridization used to create the seedless variety.