Fig. 5.2-1. Transverse section of wood of ivy (Hedera) with living fibers. Many sclerenchyma cells die soon after they reach their mature size and have lignified their wall, but some remain alive for a long time. Of course, all are alive while they are still growing and differentiating. This sample of ivy wood shows fibers (thick, red-stained wall) that have nuclei (gray, arrows), and many even have starch grains. Notice that several of the fibers appear to have smooth, blue-green contents -- that is actually a non-lignified primary wall that divides the fiber cross-wise into an upper and lower cell -- these are septate fibers.