SECRETORY-TISSUES OF THE FLOWER OF SANANGO-RACEMOSUM (GESNERIACEAE) -I - LIGHT-MICROSCOPY

Sanango racemosum (Ruiz & Pav.) Barringer has a dry stigma without a f ree-flowing secretion fluid but with a hydrated proteinaceous pellicle . The stigmatic surface is covered with unicellular, bottle-shaped pap illae. At maturity, a viscous emulsion is accumulated between the cuti cle and the pecto-cellulosic wall of the papillae, causing it to becom e detached from the surface of the papilla cell walls, The style has a central solid core of transmitting tissue. The cells of the transmitt ing tissue are rich in starch and exhibit thick lateral walls rich in pectic substance. The nectary disk is a ring elongated into a cup, wit h five lobes at the top, One of the most conspicuous histological feat ures of the disk is the abundance of starch in the secretory cells. Th e disk is supplied only by phloem; the stomata are found in the top of the lobes. A fluid substance is produced just before anthesis and sec reted through the stomata with no visible decline in starch level. Dur ing anthesis and after fertilization, a rapid decline in starch is obs erved. The hypothesis that the disk has other functions besides that o f a nectary is discussed.