OVULE AND FUNICLE MORPHOLOGY

Ovules are hemiorthotropous or orthotropous (Grayum, 1991), rarely hemianatropous (Mayo et al, 1997) and are bilaterally symmetrical with an eccentric attachment of the funiculus (French, 1986). Those which are solitary or few per locule are either basal or sub-basal, while those which are numerous in each locule are usually axillary along the sides of the locule. The funicles are usually as long as or longer than the ovules. Those ovules which are axillary usually have funicles of different lengths since they are positioned increasingly higher on the axis. After meeting with the wall of the locule the funicle is lightly fused to the wall all the way to the base and can be easily removed intact by pulling it free. This might argue against the assumption by Mayo (1989) that basal and sub-basal placentation was derived from axile placentation. While no anatomical study was made of this phenomenon, the frequent presence of funicles of axile placentas which arose from the base makes it appear that at least in the case of some Central American species of P. subg. Philodendron, species with axile placentation may have evolved from species with basal or sub-basal placentas.

The funicle of P. subg. Philodendron is frequently densely covered with short, usually inconspicuous, gland-like trichomes from near the base, sometimes extending to about half its total length. The secretory trichomes are continuous with those of the placentas and lining of the stylar canals (Mayo, 1989). The funicles of a single ovary are usually not of equal length if the ovules are basal or sub-basal since the ovules are usually positioned at slightly different heights off the floor of the locule. Even when the ovules are scattered along much of the length of the axis of the locule wall, the funicles are of slightly different sizes. In reality they are often of radically different length from one another when pulled free to the base of the locule where many seem to arise. In many cases the funicles can easily be pulled free from the locule walls where they appear to be only loosely adhering.