ANDROECIUM
The androecium is truncate at the apex, prismatic to obpyramidal and usually irregularly 4-5-sided (Fig. 30). It consists of 2-6 sessile stamens (mostly 3-4). They are always free from one another although often weakly fused at the base into a floral receptacle. Stamen number varies within a single spadix and is never constant (Mayo, 1986). Despite the clear grouping of stamens it is sometimes difficult to discern clear floral groupings, especially when the androecium lacks a floral receptacle and when the stamens are not fully extrorse. Mayo (loc.cit.) reported that some species have stamens that are directed laterally rather than extrorsely.The androecia range from 2 to 6 mm diam. and show little variation from species to species. Stamens of all species studied by Mayo (loc.cit.) had druses in their apices. Anthers are sessile to subsessile with a thick connective which is truncate at the apex and overtops the thecae. The connective of all species studied by Mayo (loc.cit.) had raphides present. The thecae are ellipsoid, oblong or linear, emarginate at the base, and each opens by a short lateral slit or by a subapical pore. The two thecae of a stamen are generally adjacent in P. subg. Philodendron but generally positioned far apart in P. subg. Pteromischum and P. subg. Meconostigma. Anther thecae lack cell wall thickenings in the endothecium in P. subg. Philodendron (present only in P. goeldii and P. leal-costae 2 unusual members of P. subg. Meconostigma in South America) (French, 1985).
Pollen emerges in slender somewhat viscid filaments (Fig. 31). These slender strands of pollen do not persist for many hours and ultimately the pollen becomes matted in irregular clusters (Fig. 391, P. straminicaule).
In P. subg. Philodendron resin canals in the staminate portion of the spadix are situated beneath the stamens and secrete resin onto the surface of the stamens. The same is not true of P. subg. Pteromischum and P. sect. Meconostigma where the resin canals are borne at a deeper level in the axis and do not secrete nectar onto the surface of the stamens (Mayo, 1986) (Fig. 128, P. crassispathum).
French (1986a) reported that the vasculature of most species of P. subg. Philodendron consists of a single forked bundle with widely divergent branches. Carvell (1989) reports that a single unbranched trace supplies each stamen. In contrast, members of P. subg. Meconostigma have traces that lack branches or have only short branches that spread at an acute angle. Pollen is shed through short lateral slits or by a subapical pore in each theca, typically emerging in long, slender filamentous strands. See section on "Pollination" for a description of its emergence.
Stamens have both druses and raphide idioblasts with secondarily thickened walls and tanniniferous idioblasts occurring throughout the ground tissue (Carvell, 1989).
