Sentence:  All flowers in a head share a common <WSD>receptacle</WSD>. The <WSD>receptacle</WSD> may be flat or convex. It may bear tiny scales called paleae. The paleae of a <WSD>receptacle</WSD> are referred to as chaff. <WSD>Receptacles</WSD> without paleae are said to be epaleate or naked. When the paleae are shed, they may leave either a smooth or a pitted <WSD>receptacle</WSD>. Occasionally, hairs, scales, or bristles may also be present on the <WSD>receptacle</WSD>. 
Meaning of the word marked with <WSD> tags:  In the Asteraceae (aster or sunflower family), the end of the peduncle to which all of the florets of the flower head are attached.