416 



THE VASCULAR PLANTS 



on from season to season, putting up new leaves. These 

 large leaves of the true ferns are sometimes called fronds. 

 They have distinct veins. You recall that the leaves of 

 mosses have no veins. Veins are a part of the vascular 

 system. The veins of ferns differ from those of seed plants 

 in that they branch by forking ; that is, one vein divides 



Fig. 207. — Ferns growing abundantly in moist woods. Note the large, compound 

 leaves. It is evident that they do not require strong illumination. 



into two equal veins. (See Figure 208.) In spring you 

 may have noticed that the young leaves of ferns are coiled 

 in a roll; they gradually uncoil. (See Figure 209.) By 

 this habit as well as by their venation (vein arrangement) 

 fern leaves are easily identified. 



A cross section of the stem or the petiole of a true fern 

 shows the well-developed vascular system. (See Figure 210.) 

 You note that the xylem and phloem do not occur in bun- 

 dles such as you saw in seed plants. In the stem which is 



