They also secrete a waxy, transparentsubstance called cutin.
它们还分泌蜡质的透明物质，称作角质。
2
When the substance is only a few of these layers thick, though, it is known as graphene and is transparent.
当形成的物质达到几个碳原子层的厚度时，便形成了被称为石墨吩的透明物质。
3
An ultrathin panel comprised of stacking a plurality of glass sheets, which may be coated with a transparent cladding substance or may be uncoated, fastened together using an epoxy or adhesive.