STYLE AND STIGMA MORPHOLOGY

This treatment has followed the classification of styles and stigmas defined by Mayo (1989). Although there is considerable diversity at the microscopic level, much of this is easily visible only by dissection (see section entitled "Style Types"). The fresh styles of P. subg. Philodendron are relatively uniform microscopically. Usually they are hemispherical or sometimes globose or depressed-globose. The microscopically visible portion is the stigma, a "single continuous area in which the epidermal cells are greatly elongated into secretory papillae" (Mayo, 1986). This dense layer of stigmatic papillae are so closely packed and so engulfed in a gelatinous fluid as to appear almost as a solid. Still, a needle can be passed easily across and through much of its apparent mass in any direction without disturbing its shape. The stigmatic papillae are slender, many times longer than broad and are attached to the surface of sessile, funnel-shaped, flat or lobulate stigma and are chiefly hemispherical and discoid and sometimes lobulate stigma. Mayo (loc.cit.) reports that the stigmatic papillae often contain tannin cells.

The stigmatic papillae typically dry to form a thin, flat, often translucent, wafer-like apron around the now somewhat visible style apex. In time the stigmatic apron may fall off altogether allowing easy inspection of the style apex. Sometimes the stigma dries erect and disheveled. In these cases the appearance of the stigmas is more difficult to determine but, regardless of how the stigma dries, the style apex often can be made easily visible on a dried specimen by lightly scraping away the stigmatic papillae. The complexities of the style types of Philodendron is discussed below.