Unidentified fruit seedlings germinating in the guano (dried excrement of fish-eating sea birds used as a fertilizer) beneath an oilbird colony in Aripo cave, Trinidad. Oilbirds feed on fruit of forest trees at night & when they return to the cave they void the seeds onto the guano pile . The seeds germinate but fail to grow properly due to lack of light. Light has a profound effect on the development of plants. It affects photosynthesis & the synthesis of chlorophyll. Growing a plant in semi-darkness (as here) results in etiolation; the plant is pale yellow owing to lack of chlorophyll, the stem is elongated & the leaves fail to expand.