The refractive index of ice crystals depends upon the polarization and propagation direction of a beam of light .
冰晶的折射率取决于一束光线的偏振和传播方向。
The argument goes like this . Many plants depend on fire for their propagation .
论证如下：很多植物依靠火焰繁殖。
I am careful to point this out , because it 's easy to mistake them for an organisation dedicated to the promotion of sex with vegetables or the propagation of self-loathing , misogyny and pamela anderson .
