1. The hydrophilic proteinaceous matrix of *chloroplasts
. It contains the enzymes and reagents necessary for the dark reactions of photosynthesis.
2. (pl. stromata) A solid mass of plectenchyma that may bear perithecia either on its surface, as in Nectria cinnabarina (coral-spot fungus), or embedded within the tissue with only the ostioles appearing at the surface, as in Xylaria hypoxylon (candle-snuff fungus).