1·But the very end of such a network, the leaf, has a different architecture. Unlike the xylem and phloem, the veins in a leaf cross-link and loop.
但网络的最边缘——叶子，却具有不同的结构，与木质部和韧皮部不同，叶子的纹路交叉并成环。
2·Roads, railways, water and gas mains, sewage pipes and electricity cables all move things around. So do the blood vessels of animals and the sap-carrying xylem and phloem of plants.
他的观点是，在某种程度上二者均由运输物质的网络构成——公路，铁路，水路以及煤气管，污水管还有电缆线都在输送物质，动物血管和植物运输汁液的木质部、韧皮部也是如此。
3·The xylem of ferns and conifers contains only tracheids.
蕨类植物和针叶树的木质部仅含有管胞。
4·In older stems, only the most recent rings of xylem participate in the transport of materials. these make up the sapwood.
在老茎中，仅最新的木质部环参与物质的运输。这些木质部环组成边材。
5·The stele includes all primary tissues derived from the procambium consists of pericycle, phloem and xylem.
中柱包括从原形成层衍生而来的全部初生组织，由中柱鞘、韧质部和木质部组成。