BOTN 201 - Department of Biology Herbarium - TAMU
Images of the Navasota Flora - 23 July 1995
Only the most hardy elements of the Navasota Flora are reproductively active during the 'high summer' period. One of these, Croton capitatus (Euphorbiaceae), known locally as 'doveweed, wooly croton, or hogweed', represents a lineage of the Spurge Family that is quite large (ca. 800 species), diverse (herbs, shrubs, trees), and distributed worldwide. Typical of its family, C. capitatus is monoecious with pistillate flowers on the mature to form a triloculate capsule with one seed per locule. carunculate, i.e., they show an outgrowth (caruncle) from the integuments (seed coat) at or near the hilum (funiculus [ovule stalk] scar). This outgrowth, usually rich in nutrients (lipids, oils), is produced as an 'offering' for possible dispersal vectors. When these are ants, which appears to be the case with C. capitatum (masses of seeds accumulate at Harvester Ant mounds this time of year), the caruncle is also termed an elaiosome.
Local Mexican Plum (Prunus mexicana - Rosaceae) populations are now producing plums. These began with gynoecium to produce a drupe. This fruit type, characteristic of the subfamily Prunoideae features differentiation of the pericarp into three tissue types. The outer exocarp (which carries a waxy coating or mesocarp. The latter, functioning like the elaiosome of Croton capitatus attracts dispersal vectors. However, since these are usually not ants, the innermost layer of pericarp differentation, the endocarp provides a hard, lignified protective covering for the seed. Thus, as is the case with all Prunus species (Plum, Peach, Almond, Cherry) the fruit carries an internal 'stone' or 'pit' or - botanically - a pyrene.
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Last updated by HDW on 27 July 1995