0 a layer of long cells between two thin surface layers of a leaf, containing a lot of chloroplasts (= the parts of a cell where energy from the sun is turned into food) -- 栅状层
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
再长的路,一步步也能走完,再短的路,不迈开双脚也无法到达。