abstract biology Capsella Capsella bursa-pasto embryo enlargment family Brassicaceae magification micro microscope mustard plant seed Shepherd's-purse aerogramme background blue color coloration colored colour coloured fine light light-blue light-weight paper stationery thin coal dark details grunge grungy heavy industrial lamp loc locomotive metal old steam train transport transportation board decay Dirt dirty door paint painted painting plank red rusty saavem texture urban wood design lumber pattern rust rustic surface timber tree trunk wooden backdrop colorful colors colourful colours stripes structure structures textures vertical wall wallpaper